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A fused-ring based electron acceptor for efficient non-fullerene polymer solar cells with small HOMO offset
Soochow University, Peoples R China; Chinese Academic Science, Peoples R China.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
Chinese Academic Science, Peoples R China; University of Chinese Academic Science, Peoples R China.
Soochow University, Peoples R China.
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2016 (English)In: NANO ENERGY, ISSN 2211-2855, Vol. 27, 430-438 p.Article in journal (Refereed) Published
Abstract [en]

A non-fullerene electron acceptor bearing a novel backbone with fused 10-heterocyclic ring (in-dacenodithiopheno-indacenodiselenophene), denoted by IDTIDSe-IC is developed for fullerene free polymer solar cells. IDTIDSe-IC exhibits a low band gap (E-g=1.52 eV) and strong absorption in the 600850 nm region. Combining with a large band gap polymer J51 (E-g=1.91 eV) as donor, broad absorption coverage from 300 nm to 800 nm is obtained due to complementary absorption of J51 and IDTIDSe-IC, which enables a high PCE of 8.02% with a V-oc of 0.91 V, a J(SC) of 15.16 mA/cm(2) and a FF of 58.0% in the corresponding PSCs. Moreover, the EQE of 50-65% is achieved in the absorption range of IDTIDSe-IC with only about 0.1 eV HOMO difference between J51 and IDTIDSe-IC. (C) 2016 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV , 2016. Vol. 27, 430-438 p.
Keyword [en]
Non-fullerene acceptor; Indacenodithiophene; Polymer solar cells
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:liu:diva-132487DOI: 10.1016/j.nanoen.2016.07.019ISI: 000384910500047OAI: oai:DiVA.org:liu-132487DiVA: diva2:1046260
Note

Funding Agencies|National Natural Science Foundation of China [21504062, 21572152]; China Postdoctoral Science Foundation [2015M581853]; Jiangsu Province Postdoctoral Science Foundation [1501024B]; Vinnova [2015-04751]; China Scholarship Council (CSC) [201306730002]; Swedish Research Council (VR) [621-2013-5561]; Swedish Energy Agency [EM 42033-1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Collaborative Innovation Center of Suzhou Nano Science and Technology; Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)

Available from: 2016-11-13 Created: 2016-11-12 Last updated: 2017-08-18
In thesis
1. Studies of Voltage Losses in Organic Solar Cells
Open this publication in new window or tab >>Studies of Voltage Losses in Organic Solar Cells
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic photovoltaic (OPV) devices based on semiconducting polymers and small molecules are potential alternatives to inorganic solar cells, owing to their advantages of being inexpensive, lightweight, flexible and suitable for roll-to-roll production. The state of art organic solar cells (OSCs) performed power conversion efficiencies (PCEs) over 13%.

The quantum efficiency losses in OSCs have been significantly reduced within the charge generation and extraction processes, resulting in high EQEPV (70-90%) and high FF (70-80%). Whereas, large voltage losses (Δ𝑉 = 𝐸𝑔/𝑞 − 𝑉𝑂𝐶) were observed in conventional fullerene based solar cells, and it has been the main limiting factor for further OPV advancement. Therefore, strategies to reduce the voltage losses are required.

In this thesis, newly designed non-fullerene (NF) acceptors are used to construct novel material systems for high efficiency solar cells. In particular, we studied the hole transfer in these fullerene free systems. We also reported a NF system that exhibit ultrafast and efficient charge separation despite a negligible driving force, as ECT is nearly identical to 𝐸𝑔. Moreover, the small driving force is found to have minimal detrimental effects on charge transfer dynamics of the OSCs. We demonstrate a NF based OSC with efficiency of 9.5% and internal quantum efficiency nearly 90% despite a low voltage loss of 0.61 V. This creates a path towards highly efficient OSCs with a low voltage loss.

CT states in OSCs are also investigated, since VOC is governed by the CT energy (ECT), which is found as 𝑞𝑉𝑂𝐶 = 𝐸𝐶𝑇 − 0.6 in a large set of fullerene based solar cells. In order to reduce these recombination losses from CT states, we explored polymer-diPDI systems which exhibited weakened D-A coupling strength, due to the steric hindrance effect. The radiative recombination losses at D/A interface in these NF devices are all reduced to less than 0.18 eV. In particular, in some cases, the additional emission from pure material is favorable for suppressing the non-radiative CT states decay. Consequently, the recombination losses in these NF systems are reduced to 0.5 eV, while the charge generation is still efficient as confirmed by PL quenching and EQEPV.

Novel material systems based on non-fullerene acceptors are investigated. The systems performed energy offsets (ΔHOMO or ΔLUMO) less than 0.15eV, resulting in the same energy of CT states and bulk excitons. In this regard, the charge transfer energy loss is minimized. We also found that the EL spectra as well as the EQEEL of the blend solar cells are similar with that of lower gap components in blends. Thus the non-radiative voltage losses are reduced to < 0.3V and small voltage loss of 0.5-0.7V are obtained. Meanwhile, the charge generation in systems are still efficient and high EQEPV of 50-70% can be achieved. It confirms that there is no intrinsic limit for the VOC and efficiency of OPVs as compared with other photovoltaic technologies.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 63 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1872
National Category
Condensed Matter Physics Energy Engineering Physical Sciences
Identifiers
urn:nbn:se:liu:diva-139868 (URN)9789176854747 (ISBN)
Public defence
2017-09-15, Schrödinger, Fysikhuset, Campus Valla, Linköping, 10:26 (English)
Opponent
Supervisors
Note

Funding: China Scholarship Council (CSC).

Available from: 2017-08-18 Created: 2017-08-18 Last updated: 2017-08-18Bibliographically approved

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