Alkali-metal incorporation is widely employed to improve the performance and stability of organic halide perovskites, yet the underlying doping mechanisms and diffusion pathways remain poorly understood. Here, we use ultraviolet photoemission spectroscopy to probe the evolution of the electronic structure of CH3NH3PbX3 (X = I, Br, and Cl) single crystals upon potassium and cesium deposition. We observe two distinct regimes governed by halide chemistry: facile bulk diffusion in CH3NH3PbI3 and CH3NH3PbBr3, in contrast to surface-confined accumulation in CH3NH3PbCl3, arising from kinetically hindered alkali migration in the chloride perovskite. Temperature-dependent measurements of the doped crystals further detect opposite valence band shifts for CH3NH3PbBr3 relative to CH3NH3PbI3 and CH3NH3PbCl3, highlighting the role of surface termination and charge redistribution. Notably, alkali metal deposition induces substantial energy level shifts while leaving band dispersions largely unchanged, indicating a predominantly interfacial doping mechanism. These results establish a direct link among halide composition, diffusion behavior, and electronic structure evolution, providing microscopic insight into alkali-metal interactions in perovskites.

Conventional energetic design rules for ternary organic solar cells (OSCs) often overlook interfacial potential shifts, leading to an incomplete understanding of energy-level alignment (ELA) based on the idealized vacuum-level assumption. In this work, we reveal that these hidden potential steps, together with the formation of an alloy donor morphology, are the key to unlocking high-performance ternary blends. By utilizing the monolayer-by-monolayer Langmuir-Schaefer method combined with photoelectron spectroscopy, we directly characterized the ELA at each donor and acceptor interface within the ternary blends. We show that the two donors, possessing complementary absorption profiles, exhibit synchronized contact-induced potential steps at their respective interfaces with the acceptor. This potential compensation precisely offsets the intrinsic HOMO offsets measured in neat films, resulting in a fully aligned and unified HOMO-level landscape across the ternary blend. This configuration provides the physical solution to reconcile efficient charge generation with a maximized photovoltaic gap. Our findings highlight that integrating morphological alloying with synchronized potential compensation provides a robust framework for understanding and rationally engineering the complex electronic landscapes of multi-component OSCs.

Covalent organic frameworks (COFs) show great promise for photocatalytic hydrogen production due to their tunable electronic structures and functionalities. However, the high exciton binding energy and insufficient charge separation capabilities limit the COFs' photocatalytic efficiency. Herein, we performed molecular-level functionalization by introducing hydroxyl or methoxy groups into the COF, and explored in depth the impact of hydroxyl functionalization on the photogenerated carrier behavior in the COF. Through detailed experimental and theoretical studies, we reveal that the introduction of hydroxyl groups could enhance charge separation and stabilization, effectively suppressing the recombination of photo-generated electron-hole pairs, and thereby reducing exciton binding energy. As a result, the HITMS-COF-3 with fully hydroxyl substitutes achieves a hydrogen production rate over 65,310 & micro;mol g-1 h-1 with a quantum yield of 6.9% at 520 nm, which is a 3.7-fold increase compared to those obtained with fully mehoxyl substituted COF (HITMS-COF-1). HITMS-COF-3 also achieves a higher electron transfer number (0.46 e-) and a prolonged excited state lifetime (approximate to 2 ns). The results indicate that modulating the COFs chemical microenvironment provides valuable insights into solar fuels with efficient organic photocatalysts.

Polarization detection enhances signal contrast and is widely utilized in diverse advanced applications. An ongoing challenge is the development of high-performance polarization-sensitive photodetectors based on optically anisotropic organic semiconductors, particularly in the near-infrared (NIR) region. While uniaxially aligned pi-conjugated polymers with high aspect ratios exhibit strong linear dichroism and have shown promise, their limited NIR performance and heavy reliance on polymer material now represent critical limitations. Here, a breakthrough is reported in achieving giant linear dichroism and exceptional polarization detection with low aspect-ratios (AR) non-fullerene small-molecule (NFSM) acceptors, extending polarization sensitivity from the UV-vis to the NIR range. An impressive dichroic ratio of 27.1 at 605 nm and 12.0 at 780 nm is demonstrated. The maximum polarization photocurrent ratio is 11.2 at 780 nm under parallel versus perpendicular polarized light. This unprecedented performance originates from synergistic molecular alignment, wherein NFSMs significantly enhance the uniaxial orientation of both the polymer matrix and the NFSMs themselves during self-assembly and thermal annealing. Besides, such a linear-polarization-sensitive photodetectors (LPS-PDs) are showcased in generating degree-of-linear-polarization imaging. The work establishes NFSMs as a viable material system for next-generation of organic LPS-PDs and provides fundamental insights into structural origins of polarization sensitivity in low AR organic semiconductors.

An efficient oxygen reduction reaction (ORR) is crucial for deoxygenation electrolyzers. However, the use of metal catalysts in electrolyzer designs is challenging due to their high cost, catalyst dissolution, and susceptibility to poisoning. Conductive polymers have emerged as a promising new class of metal-free catalysts for ORR, combining electron conductivity and a lack of an insulating oxidation layer. In this study, a new n-type polymer is explored, poly(benzimidazobenzophenanthroline) (BBL), as an ORR catalyst to enhance deoxygenation efficiency in carbon-based electrolyzers. Electrocatalytic studies show that BBL film improves ORR kinetics via a four-electron pathway with a mass activity of the order of 100 A g-1. A low-voltage electrolyzer is constructed and tested using BBL-coated carbon fiber paper (CFP) as the cathode for ORR and CFP as the anode to drive the oxidation of catechol as a compensating faradaic reaction to facilitate ORR. The deoxygenation electrolyzer with a drop-cast BBL cathode achieves fast deoxygenation kinetics, reaching below 0.1 mg L-1 DO in salty solution with 0.001 m catechol. The findings introduce a new approach to deoxygenating thermal fluids by employing an ORR polymer catalyst and a compensating redox additive (RA) in water.

Reducing heterointerface nonradiative recombination is a key challenge for realizing highly efficient perovskite solar cells (PSCs). Motivated by this, a facile strategy is developed via interfacial energetics reversal to functionalize perovskite heterointerface. A surfactant molecule, trichloro[3-(pentafluorophenyl)propyl]silane (TPFS) reverses perovskite surface energetics from intrinsic n-type to p-type, evidently demonstrated by ultraviolet and inverse photoelectron spectroscopies. The reconstructed perovskite surface energetics match well with the upper deposited hole transport layer, realizing an exquisite energy level alignment for accelerating hole extraction across the heterointerface. Meanwhile, TPFS further diminishes surface defect density. As a result, this cooperative strategy leads to greatly minimized nonradiative recombination. PSCs achieve an impressive power conversion efficiency of 25.9% with excellent reproducibility, and a nonradiative recombination-induced qVoc loss of only 57 meV, which is the smallest reported to date in n-i-p structured PSCs.

Tandem solar cells have gained significant attention due to their rapid advancements in power conversion efficiency (PCE) and their potential to exceed the detailed balance limit of single-junction solar cells. However, despite ongoing progress in perovskite-silicon tandem solar cells, all-perovskite tandem solar cells (APTSCs) still lag their perovskite-silicon counterparts. This raises the question: can further development close this gap? Upon theoretical modeling combining optical and electrical calculations, we found that: i) the PCE limitations in APTSCs are primarily caused by the reflection losses at the top perovskite interface; ii) introducing random texturing at the surfaces of wide-bandgap perovskites plays a critical role in enhancing light absorption, which can potentially improve PCE up to 30.97%. This improvement can be attributed to the reduced reflection and increased absorption at both the top wide-bandgap and the bottom narrow-bandgap perovskites. Furthermore, comparison between the calculated results and the experimental data clearly highlights the importance of light management strategies, particularly in improving the short-circuit current density. This approach is more effective than relying solely on interfacial passivation and energy band alignment to enhance the open-circuit voltage. The findings will provide valuable theoretical insights for optimizing and advancing the performance of APTSCs.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a benchmark hole-transporting (p-type) polymer that finds applications in diverse electronic devices. Most of its success is due to its facile synthesis in water, exceptional processability from aqueous solutions, and outstanding electrical performance in ambient. Applications in fields like (opto-)electronics, bioelectronics, and energy harvesting/storage devices often necessitate the complementary use of both p-type and n-type (electron-transporting) materials. However, the availability of n-type materials amenable to water-based polymerization and processing remains limited. Herein, we present a novel synthesis method enabling direct polymerization in water, yielding a highly conductive, water-processable n-type conjugated polymer, namely, poly[(2,2 '-(2,5-dihydroxy-1,4-phenylene)diacetic acid)-stat-3,7-dihydrobenzo[1,2-b:4,5-b ']difuran-2,6-dione] (PDADF), with remarkable electrical conductivity as high as 66 S cm(-1), ranking among the highest for n-type polymers processed using green solvents. The new n-type polymer PDADF also exhibits outstanding stability, maintaining 90% of its initial conductivity after 146 days of storage in air. Our synthetic approach, along with the novel polymer it yields, promises significant advancements for the sustainable development of organic electronic materials and devices.

Photoelectrochemical (PEC) water splitting is a promising approach to directly convert solar energy to renewable and storable hydrogen. However, the very low photovoltage and serious corrosion of semiconductor photoelectrodes in strongly acidic or alkaline electrolytes needed for water splitting severely impede the practical application of this technology. In this work, we demonstrate a facile approach to fabricate a high-photovoltage, stable photoanode by depositing Ni(OH)(2) cocatalyst on cubic silicon carbide (3C-SiC), followed by aging in 1.0 M NaOH at room temperature for 40 h without applying electrochemical bias. The aged 3C-SiC/Ni(OH)(2) photoanode achieves a record-high photovoltage of 1.10 V, an ultralow onset potential of 0.10 V vs the reversible hydrogen electrode, and enhanced stability for PEC water splitting in the strongly alkaline solution (pH = 13.6). This aged photoanode also exhibits excellent in-air stability, demonstrating identical PEC water-splitting performance for more than 400 days. We find that the aged Ni(OH)2 dramatically promotes the hole transport at the photoanode/electrolyte interface, thus significantly enhancing the photovoltage and overall PEC performance. Furthermore, the oxygen evolution reaction (OER) activity and the phase transitions of the Ni(OH)(2) electrocatalyst before and after aging are systematically investigated. We find that the aging process is critical for the formation of the relatively stable and highly active Fe-doped beta-NiOOH, which accounts for the enhanced OER activity and stability of the PEC water splitting. This work provides a simple and effective approach to fabricate high-photovoltage and stable photoanodes, bringing new premise toward solar fuel development.

Low temperature hydrothermal methods have been utilized to synthesize Hematite/Zinc oxide alpha-Fe2O3/ZnO composite nano-heterojunction nanorods grown on FTO glass substrates while monitoring the effect of different concentrations of urea on the morphology of the composite nano-heterojunction. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used for the structural characterization of the alpha-Fe2O3/ZnO different samples. UV-visible spectroscopy was used for the characteristic absorbance versus wavelength of alpha-Fe2O3/ZnO composite nano-heterojunction which shows an absorption edge from 400 to 560 nm. X-ray photoelectron spectroscopy (XPS) technique was applied to study of chemical composition of the alpha-Fe2O3/ZnO and the obtained information demonstrated a pure phase alpha-Fe2O3/ZnO has been achieved. The best efficiency among urea concentrations for the best composite nano-heterojunction sample was achieved when using 0.2 M of urea. The electrochemical properties of the composite nano-heterojunction were investigated using a three-electrode electrochemical cell. Estimation of the electrochemical area shows that both the composite nano-heterojunction and the bare alpha-Fe2O3 have similar values. This confirms that the enhanced electrochemical property of the composite nano-heterojunction is due to a synergetic effect as expected.