Selective electron transport and extraction are essential to the operation of photovoltaic devices. Electron transport layer (ETL) is therefore critical to organic photovoltaics (OPV). Herein, an ETL configuration is presented comprising a solution-processed n-n organic heterojunction to enhance electron transport and hole blocking, and boost power conversion efficiency (PCE) in OPV. Specifically, the n-n heterojunction is constructed by stacking a narrow-band n-type conjugated polymer layer (PNDIT-F3N) and a wide-band n-type conjugated molecule layer (Phen-NaDPO). Based on the ultraviolet photoelectron spectroscopy measurement and numerical simulation of current density-voltage characteristics, the formation of the built-in potential is investigated. In three OPVs with different active layers, substantial improvements are observed in performance following the introduction of this ETL configuration. The performance enhancement arises from the combination of selective carrier transport properties and reduced recombination. Another contributing factor is the good film-forming quality of the new ETL configuration, where the surface energies of the related materials are well-matched. The n-n organic heterojunction represents a viable and promising ETL construction strategy for efficient OPV devices.

The unique properties and potential optoelectronic applications of two-dimensional molecular crystals (2DMCs) of organic semiconductors make them fascinating research subjects. With advancements in crystal engineering, it is becoming reality to produce 2DMCs with molecular-level thickness and large areas up to the centimeter scale, enabling us to directly explore the electronic structure of 2DMCs and to correlate them with their electrical properties. Here, we investigated the electronic structure of 2DMCs of C6-DPA using photoemission spectroscopy and electrical properties based on organic field-effect transistors. Our findings indicate that anisotropic band dispersion is present in the ab plane of the 2DMCs of C6-DPA which is in good agreement with the in-plane anisotropic mobility, i.e., the direction of the strongest molecular overlap coincides with the direction of the highest mobility.

Due to a threat to human life from heavy metal ions pollution, unprecedented interest has been gained in the development of water purification technologies. Here, we explore another new approach to exploit a prospective carbon material for removing copper ions from aqueous solution based on rapid and easy capacitive deionization (CDI). Reasonable carbon materials modification with ideal composition and improved morphological structure is essential to additionally optimize the capabilities of CDI. We prepared a nitrogen-rich hierarchically porous carbon composites (CoFe-NC) with uniform cobalt (Co) and iron (Fe) doped metal in carbon skeleton by a simple impregnation and pyrolysis method, derived from zeolitic imidazolate framework-8, to use as highly effective CDI electrode for copper ions removal. The addition of Fe can facilitate the uniform dispersion of metals, and enable the formation of a stable carbon cage after pyrolysis. It can sufficiently expose active sites of the electrode materials and promote interfacial charge transfer, thus improving CDI electrosorption efficiency. CoFe-NC composites electrode can achieve outstanding deionization capacity (91.31 mg g-1) in 25 mg L-1 CuSO4 solu-tion. The carbon cage structure of CoFe-NC not only prevents aggregation of metals and avoids destruction of rich multistage pore system by pyrolysis, but also induces a faster ions transport rate. In addition, density functional theory calculations demonstrated that the co-doping of Co and Fe can remarkably increase the adsorption en-ergies of Cu2+ ions, leading to excellent selectivity, which indicates that CoFe-NC composites can be a desired CDI electrode material.

Sustainable production of hydrogen gas, a green energy carrier of high density, is possible only by electrolysis of water based on the hydrogen evolution reaction (HER). Here, we report the effect of oxygen poisoning on the efficiency of hydrogen production and the consumption by the HER and the hydrogen oxidation reaction (HOR), respectively, on the interface of platinum group metal-free electrocatalyst TaS2 in pristine form and intercalated by the organic Lewis base hexylamine. The state of the surface probed by photoelectron spectroscopy was significantly altered by both Lewis base doping and oxygen poisoning. This alteration dramatically affects the hydrogen production efficiency in the HER, while the back process by the HOR was less sensitive to the changes in the surface states of the electrocatalysts. The oxygenated and intercalated electrocatalyst shows more than 2 x 105 times lower exchange current density of the HER compared to pristine oxygenated materials.

Water splitting energy production relies heavily on the development of high-performance photoelectrochemical cells (PECs). Among the most highly regarded semiconductor materials, cupric oxide (CuO) is an excellent photocathode material. Pristine CuO does not perform well as a photocathode due to its tendency to recombine electrons and holes rapidly. Photocathodes with high efficiency can be produced by developing CuO-based composite systems. The aim of our research is to develop an Ag2WO4/CuO composite by incorporating silver tungstate (Ag2WO4) nanoparticles onto hydrothermally grown CuO nanoleaves (NLs) by successive ionic layer adsorption and reaction (SILAR). To prepare CuO/Ag2WO4 composites, SILAR was used in conjunction with different Ag2WO4 nanoparticle deposition cycles. Physicochemical characterization reveals well-defined nanoleaves morphologies with tailored surface compositions. Composite CuO/Ag2WO4 crystal structures are governed by the monoclinic phase of CuO and the hexagonal phase of Ag2WO4. It has been demonstrated that the CuO/Ag2WO4 composite has outstanding performance in the PEC water splitting process when used with five cycles. In the CuO/Ag2WO4 photocathode, water splitting activity is observed at low overpotential and high photocurrent density, indicating that the reaction takes place at low energy barriers. Several factors contribute to PEC performance in composites. These factors include the high density of surface active sites, the high charge separation rate, the presence of favourable surface defects, and the synergy of CuO and Ag2WO4 photoreaction. By using SILAR, silver tungstate can be deposited onto semiconducting materials with strong visible absorption, enabling the development of energy-efficient photocathodes.

Two-dimensional, high-quality perylene single crystals were grown with a space-confined strategy method. The grown films crystallize in the alpha form, as is confirmed by a combination of techniques. Polarization -dependent optical absorption measurements show a strong anisotropy in very good agreement with the literature data, and the anisotropic mobility data in field-effect transistors document the very high crystalline order. Momentum-dependent studies using electron energy-loss spectroscopy reveal a negative dispersion of the first exciton along the crystal b direction with an exciton bandwidth of 72 meV. We argue that this behavior is a result of charge-transfer exciton coupling between the perylene dimers in the unit cell.

Understanding the possible change in UO2 surface reactivity after exposure to oxidants is of key importance when assessing the impact of spent nuclear fuel dissolution on the safety of a repository for spent nuclear fuel. In this work, we have experimentally studied the change in UO2 reactivity after consecutive exposures to O2 or gamma-radiation in aqueous solutions containing 10 mM HCO3-. The experiments show that the reactivity of UO2 toward O2 decreases significantly with time in a single exposure. In consecutive exposures, the reactivity also decreases from exposure to exposure. In gamma-radiation exposures, the system reaches a steady state and the rate of uranium dissolution becomes governed by the radiolytic production of oxidants. Changes in surface reactivity can therefore not be observed in the irradiated system. The potential surface modification responsible for the change in UO2 reactivity was studied by XPS and UPS after consecutive exposures to either O2, H2O2, or gamma-radiation in 10 mM HCO3- solution. The results show that the surfaces were significantly oxidized to a stoichiometric ratio of O/U of UO2.3 under all the three exposure conditions. XPS results also show that the surfaces were dominated by U(V) with no observed U(VI). The experiments also show that U(V) is slowly removed from the surface when exposed to anoxic aqueous solutions containing 10 mM HCO3-. The UPS results show that the outer ultrathin layer of the surfaces most probably contains a significant amount of U(VI). U(VI) may form upon exposure to air during the rinsing process with water prior to XPS and UPS measurements.

The metal-free carbon-based catalyst with low cost and high oxygen reduction reaction (ORR) activity is urgently desired to satisfy the demands of microbial fuel cells (MFCs). However, it is still a great challenge to develop a facile and feasible strategy to construct efficient active sites of heteroatom doping for carbon-based electrocatalyst. Herein, we report a strategy based on an ammonium fluoride (NH4F) gas-steamed metal-organic frameworks (MOFs) to heighten structural defects and density of N, F active sites of metal-free catalyst. Oxygen temperature-programmed deposition and density functional theory results confirm that the NH4F gas-steamed process greatly enhances the adsorption affinity of O2 and oxygen intermediates on the catalysts. The resulted N and F co-doped porous carbon cage (FNC-15) demonstrates outstanding ORR catalytic activity and long-term stability in alkaline and neutral electrolytes. This work proposes a facile and efficient in situ gas-steamed strategy to develop metal-free cathode catalysts with superior performance.

A facile gas-steamed strategy is reported for preparing heteroatom dual-doped hierarchical porous hollow carbon catalysts via carbonization of a mixture of carbon sphere precursor and ammonium fluoride (NH4F). Notably, NH4F can be decomposed into NH3 and HF by pyrolysis, in which HF gas can etch SiO2 pellets to form hollow structure while the N and F atoms can be introduced at the same time. The FCS-900 exhibits admirable elec-trocatalytic properties with the highest onset potential and limiting current density in neutral electrolytes (0.944 V vs. RHE and 6.44 mA cm-2). In comparison to MFC-Pt, much higher output voltage and power density (0.617 V and 1093.6 +/- 6.26 mW m-2) are obtained by MFC-900. Such results can be attributed to the largest specific surface area of FCS-900 to supply exposed active sites and fast transportation channels. Based on X-ray photo-electron spectroscopy, the FCS-900 catalyst possesses the active substances of pyridinic/graphitic N and C-F bonds. The synergism of N and F can effectively facilitate the adsorption of O2 during ORR, as further supported by density functional theory calculation. The facile and green synthesis strategy can be extended to design metal -free carbon-based electrocatalysts with superior electrocatalytic performance.

Organic electrochemical transistors (OECTs) are being researched for various applications, ranging from sensors to logic gates and neuromorphic hardware. To meet the requirements of these diverse applications, the device fabrication process must be compatible with flexible and scalable digital techniques. Here, we report a direct-write additive process to fabricate fully 3D-printed OECTs, using 3D printable conducting, semiconducting, insulating, and electrolyte inks. These 3D-printed OECTs, which operate in the depletion mode, can be fabricated on flexible substrates, resulting in high mechanical and environmental stability. The 3D-printed OECTs have good dopamine biosensing capabilities (limit of detection down to 6 mu M without metal gate electrodes) and show long-term (similar to 1 h) synapse response, indicating their potential for various applications such as sensors and neuromorphic hardware. This manufacturing strategy is suitable for applications that require rapid design changes and digitally enabled direct-write techniques.

Using capacitive deionization to remove heavy metal ions from water has received much attention, but the inferior salt adsorption capacity (SAC) of electrode materials has always limited its practical application. Herein, N, S co-doped two-dimensional (2D) porous glucose derived carbon nanosheets (NSPGC) was successfully fabricated, utilizing the gas exfoliation by calcination of thiourea. The NSPGC demonstrates distinct 2D lamellas, high specific surface area (2529 m2 g-1), hierarchical pore structure and high wettability. In electrochemical tests, a high specific capacitance (127 F g-1) and electrons/ions transport performance can be achieved in the NSPGC, moreover it showed a prominent SAC of 206.57 mg g-1 and recoverability in 100 mg L-1 CuSO4 solution. Moreover, the density functional theory (DFT) calculation manifested the intrinsic affinity of Cu2+ improved by N, S co-doping, which played an essential role in enhancing the Cu2+ removal performance of CDI. Our work provided a new insight into the preparation of high-performance CDI electrode materials for Cu2+ removal and promoted the application of CDI in heavy metal wastewater.

The interfacial energetics are known to play a crucial role in organic diodes, transistors, and sensors. Designing the metal-organic interface has been a tool to optimize the performance of organic (opto)electronic devices, but this is not reported for organic thermoelectrics. In this work, it is demonstrated that the electrical power of organic thermoelectric generators (OTEGs) is also strongly dependent on the metal-organic interfacial energetics. Without changing the thermoelectric figure of merit (ZT) of polythiophene-based conducting polymers, the generated power of an OTEG can vary by three orders of magnitude simply by tuning the work function of the metal contact to reach above 1000 mu W cm(-2). The effective Seebeck coefficient (S-eff) of a metal/polymer/metal single leg OTEG includes an interfacial contribution (V-inter/Delta T) in addition to the intrinsic bulk Seebeck coefficient of the polythiophenes, such that S-eff = S + V-inter/Delta T varies from 22.7 mu V K-1 [9.4 mu V K-1] with Al to 50.5 mu V K-1 [26.3 mu V K-1] with Pt for poly(3,4-ethylenedioxythiophene):p-toluenesulfonate [poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)]. Spectroscopic techniques are used to reveal a redox interfacial reaction affecting locally the doping level of the polymer at the vicinity of the metal-organic interface and conclude that the energetics at the metal-polymer interface provides a new strategy to enhance the performance of OTEGs.

The power conversion efficiency of organic solar cells (OSCs) has taken a further leap in the past three years owing to the emergence of Y6; however, their inferior stability hinders commercialization. Understanding the ambient degradation mechanism of photovoltaic materials is a key component to address this challenge. In this study, we first used in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) to investigate the effects of water, oxygen and absorbed photons on the stability of PM6 and Y6. The studied materials PM6 and Y6 show instability to oxygen and water, respectively, possibly due to the weak interaction between PM6 backbone sulphur and oxygen, and Y6 end cyano groups show instability to water. In addition, the stability of Y6 in blended PM6:Y6 films is enhanced, which is confirmed by the performance of OSCs with blended or quasi-bilayer PM6:Y6 photoactive layers. Our findings reveal PM6 and Y6 degradation on ambient exposure and predict a possible way to prevent the degradation of Y6 in OSCs.

Perovskite solar cells (PSCs) have demonstrated a high power conversion efficiency, however, the large energy loss due to non-radiative recombination is the main challenge for further performance enhancement. Here, a surface treatment strategy is developed by heat-induced decomposition of a thin interlayer 2,7-Naphthaleneditriflate (NAP) to in situ reconstruct perovskite energetics. It is verified that the reconstructed perovskite surface energetics match better with the upper hole transport layer compared to the intrinsic condition. Spontaneous generation of n/n(-) homojunctions between the perovskite film bulk and the surface region promotes hole extraction, enhancing built-in electric field, and thus significantly suppresses charge recombination at such perovskite hole-selective heterojunctions. Moreover, the surface decomposed fluorine-rich complexes passivate the defects and improve the crystallinity of the perovskite film. These advantages are confirmed by a remarkably improved efficiency from 20.52% for the control device to 23.37% for the treated one with excellent stability. The work provides a promising approach of in situ reconstructing perovskite surface and interface for the design of highly efficient and stable PSCs.

Capacitive deionization has been considered as a promising wastewater treatment technology because of its low-cost and highly efficient. Herein, we prepared hollow bowl-type carbon materials loaded with molybdenum sulfide (HBC-MoS2) composites and fabricated it as an innovative electrode material to remove Cu2+ in a multi -ion coexistence system. With the synergistic effect of electric double layer (EDL) and complexation between MoS2 and Cu2+, the HBC-MoS2-0.02 electrode achieved effective removal of copper ions from low concentration wastewater (25 mg/L) and high electrosorption capacity of 28.97 mg g-1 at 1.0 V. Even in the presence of competing ions (Na+/Zn2+/Cu2+), the HBC-MoS2-0.02 electrode still can effectively remove Cu2+ with a final adsorption capacity of 28 mg g-1, showing its superiority. The mechanism of Cu2+ removal by HBC-MoS2 is mainly due to the synergistic effect of EDL and complexation.

Harvesting indoor light to power electronic devices for the Internet of Things has become an application scenario for emerging photovoltaics, especially utilizing organic photovoltaics (OPVs). Combined liquid- and solid-state processing, such as printing and lamination used in industry for developing indoor OPVs, also provides a new opportunity to investigate the device structure, which is otherwise hardly possible based on the conventional approach due to solvent orthogonality. This study investigates the impact of fullerene-based acceptor interlayer on the performance of conjugated polymer-fullerene-based laminated OPVs for indoor applications. We observe open-circuit voltage (V-OC) loss across the interface despite this arrangement being presumed to be ideal for optimal device performance. Incorporating insulating organic components such as polyethyleneimine (PEI) or polystyrene (PS) into fullerene interlayers decreases the work function of the cathode, leading to better energy level alignment with the active layer (AL) and reducing the V-OC loss across the interface. Neutron reflectivity studies further uncover two different mechanisms behind the V-OC increase upon the incorporation of these insulating organic components. The self-organized PEI layer could hinder the transfer of holes from the AL to the acceptor interlayer, while the gradient distribution of the PS-incorporated fullerene interlayer eliminates the thermalization losses. This work highlights the importance of structural dynamics near the extraction interfaces in OPVs and provides experimental demonstrations of interface investigation between solution-processed cathodic fullerene layer and bulk heterojunction AL.

The development of highly efficient blue perovskite light-emitting diodes (PeLEDs) remains a big challenge, requiring more fundamental investigations. In this work, significant photoluminescence enhancement in mixed halide blue perovskite films is demonstrated by using a molecule, benzylphosphonic acid, which eventually doubles the external quantum efficiency to 6.3% in sky-blue PeLEDs. The photoluminescence enhancement is achieved by forming an oxide-bonded perovskite surface at grain boundaries and suppressing electron-phonon interaction, which enhances the radiative recombination rate and reduces the nonradiative recombination rate, respectively. Moreover, severe thermal quenching is observed in the blue perovskite films, which can be explained by a two-step mechanism involving exciton dissociation and electron-phonon interaction. The results suggest that enhancing the radiative recombination rate and reducing the electron-phonon interaction-induced nonradiative recombination rate are crucial for achieving blue perovskite films with strong emission at or above room temperature.

With the emergence of new materials for high-efficiency organic solar cells (OSCs), understanding and finetuning the interface energetics become increasingly important. Precise determination of the so-called pinning energies, one of the critical characteristics of the material to predict the energy level alignment (ELA) at either electrode/organic or organic/organic interfaces, are urgently needed for the new materials. Here, pinning energies of a wide variety of newly developed donors and non-fullerene acceptors (NFAs) are measured through ultraviolet photoelectron spectroscopy. The positive pinning energies of the studied donors and the negative pinning energies of NFAs are in the same energy range of 4.3-4.6 eV, which follows the design rules developed for fullerene-based OSCs. The ELA for metal/organic and inorganic/organic interfaces follows the predicted behavior for all of the materials studied. For organic-organic heterojunctions where both the donor and the NFA feature strong intramolecular charge transfer, the pinning energies often underestimate the experimentally obtained interface vacuum level shift, which has consequences for OSC device performance.

Bio-cathode Microbial electrolysis cell (MEC) has been widely discovered for heavy metals removal and hydrogen production. However, low electron transfer efficiency and heavy metal toxicity limit MEC treatment efficiency. In this study, ZIF-67 was introduced to modify Sulfate-reducing bacteria (SRB) bio-cathode to enhance the bioreduction of sulfate and Antimony (Sb) with hydrogen production in the MEC. ZIF-67 modified bio-cathode was developed from a bio-anode microbial fuel cell (MFC) by operating with an applied voltage of 0.8 V to reverse the polarity. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance were done to confirm the performance of the ZIF67 modified SRB bio-cathode. The synergy reduction of sulfate and Sb was accomplished by sulfide metal precipitation reaction from SRB itself. Maximum sulfate reduction rate approached 93.37 % and Sb removal efficiency could reach 92 %, which relies on the amount of sulfide concentration generated by sulfate reduction reaction, with 0.923 +/- 0.04 m(3) H-2/m(3) of hydrogen before adding Sb and 0.857 m(3) H-2/m(3) of hydrogen after adding Sb. The hydrogen was mainly produced in this system and the result of gas chromatography (GC) indicated that 73.27 % of hydrogen was produced. Meanwhile the precipitates were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy to confirm Sb2S3 was generated from Sb (V).

The oxygen reduction reaction (ORR) kinetics are well known to strongly rely on the activives of electro-catalysts. Herein, a Fe-N-doped porous carbon-based electrocatalyst combined with zinc (Zn)-based metal-organic frameworks (MOFs) (Fex-N@MOF) was designed and successfully fabricated via a facile process combined immersion doping and pyrolysis. By controlling the formation of Fe3C, the physical structure of porous carbon was significantly altered, and the active chemical sites of Fe species can be formed to catalyze ORR. The uniform N-doped three-dimensional interpenetrating network structure yielded a high surface area. Both Fe3C and Fe-Nx could offer an abundance of active sites and thus promoted Fe0.05-N@MOF to exhibit high ORR activity in alkaline, neutral and acid electrolytes. Fe0.05-N@MOF showed extraordinary stability and methanol tolerance under a varied pH range conditions, it could be applied as cathode elec-trocatalyst in different fuel cells such as Zn-air fuel cell (ZFC), microbial fuel cells (MFCs), as well as direct methanol fuel cell (DMFC). Fe0.05-N@MOF is a promising material to replace Pt-based electrocatalysts as non-precious metal catalysts.(c) 2023 Elsevier B.V. All rights reserved.

Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.

The heterointerfaces of charge-selective contacts are crucial in determining efficiency and stability of perovskite optoelectronic devices, where the fundamental knowledge of the buried heterointerface between perovskite and bottom charge transport layer is less well understood compared to the top interface. Herein, we systematically investigate the energetics at the perovskite/SnO2 buried heterointerface for an n-i-p perovskite solar cell (PSC) and the perovskite/PEDOT:PSS buried heterointerface for a p-i-n one, respectively. In contrast to previous cognitions, we discover a perovskite transition phase at the buried interface region that originates from the chemical bonding interaction with the bottom charge transport layer. The transition phase causes an energy level barrier and induces defects, impeding charge transport across the heterointerface. These detrimental effects trigger significant nonradiative recombination and limit the attainable device photovoltage. We then develop the energetic models that describe such buried heterointerfaces. Moreover, we further test the proposed model -derived mechanisms via inserting a thin polyvinyl alcohol layer into the buried heterointerfaces of the de-vices. We demonstrate that chemical interactions and formation of the perovskite transition phase at the buried heterointerface thereby are fully restrained, leading to a diminished electron extraction barrier and improved charge transport. As a result, significant increases in open-circuit voltage and fill factor of the devices are ach-ieved. These results will help guide future efforts on developing suitable buried heterointerfaces for superior performance of perovskite optoelectronics.

High-throughput production methods such as screen printing can bring stretchable electronics out of the lab into the market. Most stretchable conductor inks for screen printing are based on silver nanoparticles or flakes due to their favorable performance-to-cost ratio, but silver is prone to tarnishing and corrosion, thereby limiting the stability of such conductors. Here, we report on a cost-efficient and scalable approach to resolve this issue by developing screen printable inks based on silver flakes chemically coated by a thin layer of gold. The printed stretchable AgAu conductors reach a conductivity of 8500 S cm-1, remain conductive up to 250% strain, show excellent corrosion and tarnishing stability, and are used to demonstrate wearable LED and NFC circuits. The reported approach is attractive for smart clothing, as the long-term functionality of such devices is expected in a variety of environments.

Organic electrochemical transistors (OECTs) are a rapidly advancing technology that plays a crucial role in the development of next-generation bioelectronic devices. Recent advances in p-type/n-type organic mixed ionic-electronic conductors (OMIECs) have enabled power-efficient complementary OECT technologies for various applications, such as chemical/biological sensing, large-scale logic gates, and neuromorphic computing. However, ensuring long-term operational stability remains a significant challenge that hinders their widespread adoption. While p-type OMIECs are generally more stable than n-type OMIECs, they still face limitations, especially during prolonged operations. Here, we demonstrate that simple methylation of the pyrrole-benzothiazine-based (PBBT) ladder polymer backbone results in stable and high-performance p-type OECTs. The methylated PBBT (PBBT-Me) exhibits a 25-fold increase in OECT mobility and an impressive 36-fold increase in & mu;C* (mobility x volumetric capacitance) compared to the non-methylated PBBT-H polymer. Combining the newly developed PBBT-Me with the ladder n-type poly(benzimidazobenzophenanthroline) (BBL), we developed complementary inverters with a record-high DC gain of 194 V V-1 and excellent stability. These state-of-the-art complementary inverters were used to demonstrate leaky integrate-and-fire type organic electrochemical neurons (LIF-OECNs) capable of biologically relevant firing frequencies of about 2 Hz and of operating continuously for up to 6.5 h. This achievement represents a significant improvement over previous results and holds great potential for developing stable bioelectronic circuits capable of in-sensor computing.

Hydrogen technology, as a future breakthrough for the energy industry, has been defined as an environmentally friendly, renewable, and high-power energy carrier. The green production of hydrogen, which mainly relies on electrocatalysts, is limited by the high cost and/ or the performance of the catalytic system. Recently, studies have been conducted in search of bifunctional electrocatalysts accelerating both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). Herein, we report the investigation of the high efficiency bifunctional electrocatalyst TaS2 for both the HER and the HOR along with the asymmetric effect of inhibition by organic intercalation. The linear organic agent, to boost the electron donor property and to ease the process of intercalation, provides a higher interlayer gap in the tandem structure of utilized nanosheets. XRD and XPS data reveal an increase in the interlayer distance of 22%. The HER and the HOR were characterized in a Pt group metal-free electrochemical system. The pristine sample shows a low overpotential of -0.016 Vat the onset. The intercalated sample demonstrates a large shift in its performance for the HER. It is revealed that the intercalation is a potential key strategy for tuning the performance of this family of catalysts. The inhibition of the HER by intercalation is considered as the increase in the operational window of a water-based electrolyte on a negative electrode, which is relevant to technologies of electrochemical energy storage.

Air cathode microbial fuel cell (AC-MFC) cannot be used on a large scale because of its low oxygen reduction reaction (ORR) efficiency. Despite the fact that bimetallic catalysts can greatly enhance the oxygen reduction rate by regulating the electronic structure of the active site, the flaws of insufficient exposure of the active site and easy metal agglomeration limit its catalytic activity. Herein, we report on the preparation of a stable heteroatomic substrate using a copper material organic framework as a precursor, covered by Fe-based active sites. As a result of dipole-dipole interactions, the reduced product Fe2+ forms a weak Fe-O surface that is conducive to the adsorption of active substances. The presence of Fe-0 enhances the electrical conductivity of the catalytic, thus promoting ORR efficiency. Through redox coupling, the D -band center of Fe at FeCu@CN is optimized and brought close to the Fermi level to facilitate electron transfer. Notably, FeCu@CN demonstrates a superior power density of 2796.23 +/- 278.58 mW m(-3), far exceeding that of Pt/C (1363.93 +/- 102.56 mW m(-3)), in the application of microbial fuel cells (MFCs). Meanwhile, the MFC-loaded FeCu@CN maintains excellent stability and outstanding output voltage after 1000 h, which provides feasibility for large-scale application. (C) 2022 Elsevier Inc. All rights reserved.

The tremendous growth of disposable electrode-based portable devices for point-of-care testing requires mass production of disposable electrodes in a low-cost and sustainable manner. Here, we demonstrate a green route for the conversion of biomass lignin, patterning, and reduction of the lignin-derived graphene electrodes by sequential laser lithography, water lift-off and sodium borohydride (NaBH4) treatment, and their use for electrochemical lactate biosensors. Energy-saving and localized laser lithography converted the aromatic ring-rich lignin into porous laser-induced graphene (LIG). The conductivity and attachment of the LIG to the substrate were optimized in a factorial experiment with laser power and scan speed as variables. Characterization results revealed the conversion of partial heteroatoms (e.g., Na, S, O) into granular inorganic compounds on the LIG surface under laser treatment. Water was used as an eco-friendly solvent for the patterning of the LIG (P-LIG) by a lift-off process, where the inorganic residues and un-reacted lignin were dissolved, exposing the macro-/micropores in the P-LIG. NaBH4 induced a reduction of the P-LIG (P-rLIG) resulting in improved electrochemical kinetics with lower charge transfer resistance (27.3 omega) compared to the LIG (248.1 omega) and the P-LIG (61.4 omega). The porous P-rLIG served as a 3D electrode for the deposition of Prussian blue and lactate oxidase for disposable electrochemical lactate biosensors, delivering a good analytical performance towards lactate detection with a linear range up to 16 mM and a high sensitivity (1.21 mu A mM-1). These lignin-derived disposable electrodes, utilizing renewable resources together with low-energy consumption fabrication and patterning, may contribute to the sustainable manufacturing of biosensors for point-of-care and point-of-use applications.

Persistent photoconductivity (PPC) behavior in organic phototransistors has fascinating potentials in applications of photoelectronic devices. A key issue is how the presence of air affects the PPC behavior. Here, combining with the theoretical and experimental results, the PPC behavior is associated with photogenerated electrons trapped in oxygen atom-induced the reduced Lowest Unoccupied Molecular Orbitals or oxygen molecule-induced new trap state within energy bandgap of organic semiconductor. Inspired by the potential applications arising from the PPC behavior, organic memory phototransistors (OMPTs) are achieved by light programming and electrical erasing. The OMPTs show bistable current states as well as long retention times. Our results suggested that oxygen in air plays a key role in PPC behavior and provides a guidance for controlling the PPC behavior toward integrated multifunctional optoelectronic devices.

Perovskite solar cells (PSCs) suffer from significant nonradiative recombination at perovskite/charge transport layer heterojunction, seriously limiting their power conversion efficiencies. Herein, solution-processed chromium multioxide (CrOx) is judiciously selected to construct a MAPbI(3)/CrOx/Spiro-OMeTAD hole-selective heterojunction. It is demonstrated that the inserted CrOx not only effectively reduces defect sites via redox shuttle at perovskite contact, but also decreases valence band maximum (VBM)-HOMO offset between perovskite and Spiro-OMeTAD. This will diminish thermionic losses for collecting holes and thus promote charge transport across the heterojunction, suppressing both defect-assisted recombination and interface carrier recombination. As a result, a remarkable improvement of 21.21% efficiency with excellent device stability is achieved compared to 18.46% of the control device, which is among the highest efficiencies for polycrystalline MAPbI(3) based n-i-p planar PSCs reported to date. These findings of this work provide new insights into novel charge-selective heterojunctions for further enhancing efficiency and stability of PSCs.

Cathode electrocatalyst is quite critical to realize the application of microbial fuel cells (MFCs). Perovskite oxides have been considered as potential MFCs cathode catalysts to replace Pt/C. Herein, Cu-doped perovskite oxide with a stable porous structure and excellent conductivity was successfully prepared through a sol-gel method. Due to the incorporation of Cu, CaFe0.9Cu0.1O3 has more micropores and a larger surface area, which are more conducive to contact with oxygen. Doping Cu resulted in more Fe3+ in B-site and thus enhanced its binding capability to oxygen molecules. The data from electrochemical test demonstrated that the as-prepared catalyst has good conductivity, high stability, and excellent ORR properties. Compared with Pt/C catalyst, CaFe0.9Cu0.1O3 exhibits a lower overpotential, which had an onset potential of 0.195 V and a half-wave potential of 0.224 V, respectively. CaFe0.9Cu0.1O3 displays an outstanding four-electron pathway for ORR mechanism and demonstrates superiors corrosion resistance and stability. The MFC with CaFe0.9Cu0.1O3 has a greater maximum power density (1090 mW m(-3)) rather than that of Pt/C cathode (970 mW m(-3)). This work demonstrated CaFe0.9Cu0.1O3 is an economic and efficient cathodic catalyst for MFCs.

Nanostructures of conventional metals offer manipulation of light at the nanoscale but are largely limited to static behavior due to fixed material properties. To develop the next frontier of dynamic nano-optics and metasurfaces, this study utilizes the redox-tunable optical properties of conducting polymers, as recently shown to be capable of sustaining plasmons in their most conducting oxidized state. Electrically tunable conducting polymer nano-optical antennas are presented, using nanodisks of poly(3,4-ethylenedioxythiophene:sulfate) (PEDOT:Sulf) as a model system. In addition to repeated on/off switching of the polymeric nanoantennas, the concept enables gradual electrical tuning of the nano-optical response, which was found to be related to the modulation of both density and mobility of the mobile polaronic charge carriers in the polymer. The resonance position of the PEDOT:Sulf nanoantennas can be conveniently controlled by disk size, here reported down to a wavelength of around 1270 nm. The presented concept may be used for electrically tunable metasurfaces, with tunable farfield as well as nearfield. The work thereby opens for applications ranging from tunable flat meta-optics to adaptable smart windows.

Exploiting a facile way to synthesize low-cost and high-performance oxygen reduction reaction (ORR) catalysts is a core issue in microbial fuel cells (MFCs). Hence, a facile and extensible method has been developed to prepare efficient ORR catalysts by using robust UiO-66 as a precursor, modified with melamine and trithiocyanuric via the impregnation method. Benefiting from the hierarchical structure of UiO-66, the NS@UiO-66 has excellent stability, more active sites and improved mass transfer. Significantly, the half-wave potential and the current density of the NS@UiO-66 are 0.546 V vs. RHE and 6.19 mA cm(-2) respectively, which is better than that of benchmark Pt/C in neutral conditions. Furthermore, the power density of MFCs assembled with the NS@UiO-66 catalyst is 318.6 +/- 2.15 mW m(-2). The density functional theory calculation demonstrates that the reaction barrier can be reduced effectively for accelerating the ORR process through the synergistic effect of N and S. The NS@UiO-66, as an ideal candidate to substitute for the commercial Pt/C counterpart, is expected to promote the scaling-up production and application of MFCs due to low-cost elements doping and facilely synthetic method.

Fluorescent nanohybrids, based on pi-extended hydroxyoxophosphole ligands grafted onto ZnO nanoparticles, are designed and studied. The restriction of the intramolecular motions of the organic fluorophore, through either aggregates formation in solution or processing into thin films, forms highly emissive materials due to a strong aggregation induced emission effect. Theoretical calculations and XPS analyses were performed to analyze the interactions between the organic and inorganic counterparts. Preliminary results on the use of these nanohybrids as solution-processed emissive layers in organic light emitting diodes (OLEDs) illustrate their potential for lighting applications.

Plasmonic metal electrodes with subwavelength nanostructures are promising for enhancing light harvesting in photovoltaics. However, the nonradiative damping of surface plasmon polaritons (SPPs) during coupling with sunlight results in the conversion of the excited hot-electrons to heat, which limits the absorption of light and generation of photocurrent. Herein, an energy recycling strategy driven by hot-electron emission for recycling the SPP energy trapped in the plasmonic electrodes is proposed. A transparent silver-based plasmonic metal electrode (A-PME) with a periodic hexagonal nanopore array is constructed, which is combined with a luminescent organic emitter for radiative recombination of the injected hot-electrons. Owing to the suppressed SPP energy loss via broadband hot-electron emission, the A-PME achieves an optimized optical transmission with an average transmittance of over 80% from 380 to 1200 nm. Moreover, the indium-tin-oxide-free organic solar cells yield an enhanced light harvesting with a power conversion efficiency of 16.1%.

We report an efficient hole transporting layer (HTL) for organic solar cell (OSC) based on solution-processed organic-inorganic hybrid composed of ultrasonic-exfoliated MoS2 nanosheets and dopamine-copolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) derivative (DA-P). The OSCs based on this new hybrid HTL show a marked performance improvement over those with single-component HTLs, and they retain up to 80% of their original power conversion efficiency after 35 days. Our investigations reveal that the boost in performance is due to a synergistic effect that improves both hole transport and extraction ability. This effect is mainly due to the doping of exfoliated-MoS2 nanosheets on DA-P. We employ a comprehensive range of spectroscopies to uncover that the dopant is derived from the oxidation products of MoS2 nanosheets during the ultrasonic exfoliation. Our work demonstrates an efficient hybrid HTL and offers new insights into the interaction of exfoliated-MoS2 nanosheets and the PEDOT derivatives.

Ladder-type conjugated polymers exhibit a remarkable performance in (opto)electronic devices. Their double-stranded planar structure promotes an extended pi-conjugation compared to inter-ring-twisted analogues, providing an excellent basis for exploring the effects of charge localization on polaron formation. Here, we investigated alkali-metal n -doping of the ladder-type conjugated polymer (polybenzimidazobenzophe-nanthroline) (BBL) through detailed in situ spectroscopic and electrical characterizations. Photoelectron spectroscopy and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy indicate polaron formation upon potassium (K) doping, which agrees well with theoretical predictions. The semiladder BBB displays a similar evolution in the valence band with the appearance of two new features below the Fermi level upon K-doping. Compared to BBL, distinct differences appear in the UV-vis-NIR spectra due to more localized polaronic states in BBB. The high conductivity (2 S cm(-1)) and low activation energy (44 meV) measured for K-doped BBL suggest disorder-free polaron transport. An even higher conductivity (37 S cm(-1)) is obtained by changing the dopant from K to lithium (Li). We attribute the enhanced conductivity to a decreased perturbation of the polymer nanostructure induced by the smaller Li ions. These results highlight the importance of polymer chain planarity and dopant size for the polaronic state in conjugated polymers.

Achieving high-quality cesium-formamidinium lead iodide (CsxFA1_xPbI3) perovskites with tunable band gaps is highly desired for optoelectronic applications including solar cells and light -emit-ting diodes (LEDs). Herein, by utilizing an alkaline-interface-assisted cation-exchange method, we fabricate highly emissive CsxFA1_x PbI3 perovskite films with fine-tunable Cs-FA alloying ratio for emis-sion-tunable near-infrared (NIR) LEDs. We reveal that the deproto-nation of FA+ cations and the formation of hydrogen-bonded gels consisting of CsI and FA facilitated by the zinc oxide underneath effectively removes the Cs-FA ion-exchange barrier, promoting the formation of phase-pure CsxFA1_xPbI3 films with tunable emis-sions filling the gap between that of pure Cs-and FA-based perov-skites. The obtained NIR perovskite LEDs (PeLEDs) peaking from 715 to 780 nm simultaneously demonstrate high peak external quantum efficiencies of over 15%, maximum radiances exceeding 300 W sr_1 m_2, and high power conversion efficiencies above 10% at 100 mA cm_2, representing the best-performing LEDs based on solution-processed NIR emitters in a similar region.

Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2,7,7-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.

Energy level alignment (ELA) at donor-acceptor heterojunctions is of vital importance yet largely undetermined in organic solar cells. Here, authors determine the heterojunction ELA with (mono) layer-by-layer precision to understand the co-existence of efficient charge. Energy level alignment (ELA) at donor (D) -acceptor (A) heterojunctions is essential for understanding the charge generation and recombination process in organic photovoltaic devices. However, the ELA at the D-A interfaces is largely underdetermined, resulting in debates on the fundamental operating mechanisms of high-efficiency non-fullerene organic solar cells. Here, we systematically investigate ELA and its depth-dependent variation of a range of donor/non-fullerene-acceptor interfaces by fabricating and characterizing D-A quasi bilayers and planar bilayers. In contrast to previous assumptions, we observe significant vacuum level (VL) shifts existing at the D-A interfaces, which are demonstrated to be abrupt, extending over only 1-2 layers at the heterojunctions, and are attributed to interface dipoles induced by D-A electrostatic potential differences. The VL shifts result in reduced interfacial energetic offsets and increased charge transfer (CT) state energies which reconcile the conflicting observations of large energy level offsets inferred from neat films and large CT energies of donor - non-fullerene-acceptor systems.

Introduction of filler materials into organic solar cells (OSCs) are a promising strategy to improve device performance and thermal/mechanical stability. However, the complex interactions between the state-of-the-art OSC materials and filler require careful selection of filler materials and OSC fabrication to achieve lower cost and improved performance. In this work, the introduction of a natural product betulin-based insulating polymer as filler in various OSCs is investigated. Donor-acceptor-insulator ternary OSCs are developed with improved open-circuit voltage due to decreased trap-assisted recombination. Furthermore, filler-induced vertical phase separation due to mismatched surface energy can strongly affect charge collection at the bottom interface and limit the filler ratio. A quasi-bilayer strategy is used in all-polymer systems to circumvent this problem. Herein, the variety of filler materials in OSCs to biomass is broadened, and the filler strategy is made a feasible and promising strategy toward highly efficient, eco, and low-cost OSCs.

Electronic doping of conjugated semiconductor plays a critical role in the fabrication of high efficiency organic optoelectronic devices. Here, we report an organic solar cell (OSC) by doping n-type DMBI-BDZC into one host binary bulk heterojunction (BHJ) photoactive layer comprised of a polymer donor PM6 and a nonfullerene acceptor Y6. The resulting champion device yields a significantly improved power conversion efficiency from 17.17% to 18.33% with an impressive fill factor of 80.20%. It is found that the electrically doped photoactive layer exhibits enhanced and balanced charge carrier mobilities, more effective exciton dissociation, longer carrier lifetime, and suppressed charge recombination with smaller energy loss. The dopant molecule DMBIBDZC also act as a surface morphology modifier of the photoactive layer with enhanced charge transport. This work demonstrates that manipulation of charge transport via adding a low concentration dopant into photoactive layer is a promising approach for further improvement of BHJ OSC performance.

Development of photovoltaic (PV)-derived hybrid power systems can overcome the weather-dependent elec-tricity production and increase the amount of dispatchable renewable energy generation. Herein, monolithic hybrid devices are developed via rational integration of high-performance semitransparent polymer solar cells (ST-PSCs) and liquid-solid triboelectric nanogenerators (TENGs). High-performance PSCs with efficiencies of 17.4% for rigid and 15.7% for flexible devices are achieved. Further electrode modifications and integration of transparent TENGs synergistically balance the above-bandgap photon harvesting and transparency in a broad wavelength range (380 -1000 nm), yet significantly reduce the transmittance in the near-infrared wavelength range (1000 -2500 nm) of hybrid devices. The hybrid devices simultaneously provide high visible light transparency, good color fidelity, efficient heat resistance and possibility to integrate on rigid and flexible substrates. The hybrid devices attain a high solar conversion efficiency of 10.1% under 1 sun, indicating efficient light-to-electricity conversion (a maximum electrical power output: 101 W m-2) on sunny days. The hybrid devices can also generate a maximum electrical power output of 2.62 W m- 2 through waterdrop energy con-version, implying complementary green electricity production on rainy days. The controlled ambient tempera-ture and specific transmittance windows provided by the hybrid devices sustain plant growth and highlight their great potential in agricultural applications. Gratifyingly, this work demonstrates the first example of ST-PSC/ TENG hybrid systems for scaling up renewable power generation in different weather conditions, considering architectural and agricultural applications.

Organic electrochemical transistors (OECTs) have the potential to revolutionize the field of organic bioelectronics. To date, most of the reported OECTs include p-type (semi-)conducting polymers as the channel material, while n-type OECTs are yet at an early stage of development, with the best performing electron-transporting materials still suffering from low transconductance, low electron mobility, and slow response time. Here, the high electrical conductivity of multi-walled carbon nanotubes (MWCNTs) and the large volumetric capacitance of the ladder-type pi-conjugated redox polymer poly(benzimidazobenzophenanthroline) (BBL) are leveraged to develop n-type OECTs with record-high performance. It is demonstrated that the use of MWCNTs enhances the electron mobility by more than one order of magnitude, yielding fast transistor transient response (down to 15 ms) and high mu C* (electron mobility x volumetric capacitance) of about 1 F cm(-1) V-1 s(-1). This enables the development of complementary inverters with a voltage gain of >16 and a large worst-case noise margin at a supply voltage of <0.6 V, while consuming less than 1 mu W of power.

Conducting polymers, such as the p-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), have enabled the development of an array of opto- and bio-electronics devices. However, to make these technologies truly pervasive, stable and easily processable, n-doped conducting polymers are also needed. Despite major efforts, no n-type equivalents to the benchmark PEDOT:PSS exist to date. Here, we report on the development of poly(benzimidazobenzophenanthroline):poly(ethyleneimine) (BBL:PEI) as an ethanol-based n-type conductive ink. BBL:PEI thin films yield an n-type electrical conductivity reaching 8Scm(-1), along with excellent thermal, ambient, and solvent stability. This printable n-type mixed ion-electron conductor has several technological implications for realizing high-performance organic electronic devices, as demonstrated for organic thermoelectric generators with record high power output and n-type organic electrochemical transistors with a unique depletion mode of operation. BBL:PEI inks hold promise for the development of next-generation bioelectronics and wearable devices, in particular targeting novel functionality, efficiency, and power performance. The development of n-type conductive polymer inks is critical for the development of next-generation opto-electronic devices that rely on efficient hole and electron transport. Here, the authors report an alcohol-based, high performance and stable n-type conductive ink for printed electronics.

The conduction band dispersion in methylammonium lead iodide (CH3NH3PbI3) was studied by both angle-resolved two-photon photoelectron spectroscopy (AR-2PPE) with low photon intensity (similar to 0.0125 nJ/pulse) and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy dispersion of the conduction band along the Gamma-M direction was first observed by these independent methods under different temperatures, and the dispersion was found to be consistent with band calculation under the cubic phase. The effective mass of the electrons at the Gamma point was estimated to be (0.20 +/- 0.05)m(0) at the temperature of 90 K. The observed conduction band energy was different between the AR-LEIPS and AR-2PPE, which was ascribed to the electronic-correlation-dependent difference of initial and final states probing processes. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.

Defect passivation via additive and energetic modification via interface engineering are two effective strategies for achieving high-performance perovskite solar cells (PSCs). Here, the synergies of pentafluorophenyl acrylate when used as additive, in which it not only passivates surface defect states but also simultaneously modifies the energetics at the perovskite/Spiro-OMeTAD interface to promote charge transport, are shown. The additive-induced synergy effect significantly suppresses both defect-assisted recombination and interface carrier recombination, resulting in a device efficiency of 22.42% and an open-circuit voltage of 1.193 V with excellent device stability. The two photovoltaic parameters are among the highest values for polycrystalline CsFormamidinium/Methylammonium (FAMA)/FAMA based n-i-p structural PSCs using low-cost silver electrodes reported to date. The findings provide a promising approach by choosing the dual functional additive to enhance efficiency and stability of PSCs.

As a promising energy conversion equipment, the performance of microbial fuel cell (MFC) is affected by slow kinetics of oxygen reduction reaction (ORR). It is of great significance to explore electrocatalysts with high activity for sustainable energy applications. Herein, we synthesize the in-situ grown carbon nanotubes decorated electrocatalyst derived from copper-based metal organic frameworks (MOFs) co-doped with cobalt and nitrogen (CuCo@NCNTs) through straightforward immersion and pyrolysis process. The carbon nanotubes produced by metallic cobalt and high-activity bimetallic active sites formed by nitrogen doping enable CuCo@NCNTs to have the best oxygen reduction reaction (ORR) performance in alkaline electrolyte, with limit current density of 5.88 mA cm^-2 and onset potential of 0.91 V (vs. RHE). Moreover, CuCo@NCNTs nanocomposite exhibits obvious antibacterial activity, and inhibiting the biofilm on cathode surface in antibacterial test and biomass quantification. The maximum power density (2757 mW m^-3) of MFC modified with CuCo@NCNTs is even higher than Pt/C catalyst (2313 mW m^-3). In short, CuCo@NCNTs nanocomposite can be an alternative cathode catalyst for MFC.

Defect passivation is one of the most important strategies to boost both the efficiency and stability of perovskite solar cells (PSCs). Here, nontoxic and sustainable forest-based biomaterial, betulin, is first introduced into perovskites. The experiments and calculations reveal that betulin can effectively passivate the uncoordinated lead ions in perovskites via sharing the lone pair electrons of hydroxyl group, promoting charge transport. As a result, the power conversion efficiencies of the p-i-n planar PSCs remarkably increase from 19.14% to 21.15%, with the improvement of other parameters. The hydrogen bonds of betulin lock methylamine and halogen ions along the grain boundaries and on the film surface and thus suppress ion migration, further stabilizing perovskite crystal structures. These positive effects enable the PSCs to maintain 90% of the initial efficiency after 30 days in ambient air with 60%+/- 5% relative humidity, 75% after 300 h aging at 85 degrees C, and 55% after 250 h light soaking, respectively. This work opens a new pathway for using nontoxic and low-cost biomaterials from forest to make highly efficient and stable PSCs. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.