Achieving Fast Charge Separation and Low Nonradiative Recombination Loss by Rational Fluorination for High-Efficiency Polymer Solar Cells

Chenkai Sun; Fei Pan; Shanshan Chen; Rui Wang; Rui Sun; Ziya Shang; Beibei Qiu; Jie Min; Menglan Lv; Lei Meng; Chunfeng Zhang; Min Xiao; Changduk Yang; Yongfang Li

doi:10.1002/adma.201905480

Achieving Fast Charge Separation and Low Nonradiative Recombination Loss by Rational Fluorination for High-Efficiency Polymer Solar Cells

Adv Mater. 2019 Dec;31(52):e1905480. doi: 10.1002/adma.201905480. Epub 2019 Nov 14.

Authors

Chenkai Sun^{1

2}, Fei Pan^{1

2}, Shanshan Chen^{3

4}, Rui Wang⁵, Rui Sun⁶, Ziya Shang^{1

2}, Beibei Qiu^{1

2}, Jie Min⁶, Menglan Lv⁷, Lei Meng¹, Chunfeng Zhang⁵, Min Xiao⁵, Changduk Yang⁴, Yongfang Li^{1

2

8}

Affiliations

¹ Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
² School of Chemical Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
³ MOE Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, CQU-NUS Renewable Energy Materials & Devices Joint Laboratory, School of Energy & Power Engineering, Chongqing University, Chongqing, 400044, China.
⁴ Department of Energy Engineering, School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 689-798, Republic of Korea.
⁵ National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
⁶ The Institute for Advanced Studies, Wuhan University, Wuhan, 430072, China.
⁷ School of Chemical Engineering, Guizhou Institute of Technology, Guiyang, 550003, China.
⁸ Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123, China.

PMID: 31867848
DOI: 10.1002/adma.201905480

Abstract

Four low-cost copolymer donors of poly(thiophene-quinoxaline) (PTQ) derivatives are demonstrated with different fluorine substitution forms to investigate the effect of fluorination forms on charge separation and voltage loss (V_loss ) of the polymer solar cells (PSCs) with the PTQ derivatives as donor and a A-DA'D-A-structured molecule Y6 as acceptor. The four PTQ derivatives are PTQ7 without fluorination, PTQ8 with bifluorine substituents on its thiophene D-unit, PTQ9, and PTQ10 with monofluorine and bifluorine substituents on their quinoxaline A-unit respectively. The PTQ8- based PSC demonstrates a low power conversion efficiency (PCE) of 0.90% due to the mismatch in the highest occupied molecular orbital (HOMO) energy levels alignment between the donor and acceptor. In contrast, the devices based on PTQ9 and PTQ10 show enhanced charge-separation behavior and gradually reduced V_loss , due to the gradually reduced nonradiative recombination loss in comparison with the PTQ7-based device. As a result, the PTQ10-based PSC demonstrates an impressive PCE of 16.21% with high open-circuit voltage and large short-circuit current density simultaneously, and its V_loss is reduced to 0.549 V. The results indicate that rational fluorination of the polymer donors is a feasible method to achieve fast charge separation and low V_loss simultaneously in the PSCs.

Keywords: charge separation; fluorination; low-cost copolymer donors; nonradiative recombination; voltage loss.

Abstract

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