Hole Transfer Originating from Weakly Bound Exciton Dissociation in Acceptor-Donor-Acceptor Nonfullerene Organic Solar Cells

Meng-Si Niu; Kang-Wei Wang; Xiao-Yu Yang; Peng-Qing Bi; Kang-Ning Zhang; Xian-Jin Feng; Fei Chen; Wei Qin; Jian-Long Xia; Xiao-Tao Hao

doi:10.1021/acs.jpclett.9b02837

Hole Transfer Originating from Weakly Bound Exciton Dissociation in Acceptor-Donor-Acceptor Nonfullerene Organic Solar Cells

J Phys Chem Lett. 2019 Nov 21;10(22):7100-7106. doi: 10.1021/acs.jpclett.9b02837. Epub 2019 Nov 5.

Authors

Meng-Si Niu¹, Kang-Wei Wang², Xiao-Yu Yang¹, Peng-Qing Bi¹, Kang-Ning Zhang¹, Xian-Jin Feng³, Fei Chen⁴, Wei Qin¹, Jian-Long Xia², Xiao-Tao Hao^{1

5}

Affiliations

¹ School of Physics, State Key Laboratory of Crystal Materials , Shandong University , 250100 Jinan , Shandong , China.
² School of Chemistry, Chemical Engineering and Life Science, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing , Wuhan University of Technology , 430070 Wuhan , Hubei , China.
³ School of Microelectronics , Shandong University , 250100 Jinan , Shandong , China.
⁴ Department of Mechanical, Materials and Manufacturing Engineering , The University of Nottingham Ningbo China , Ningbo 315100 , P.R. China.
⁵ ARC Centre of Excellence in Exciton Science, School of Chemistry , The University of Melbourne , Parkville , Victoria 3010 , Australia.

PMID: 31682127
DOI: 10.1021/acs.jpclett.9b02837

Abstract

The underlying hole-transfer mechanism in high-efficiency OSC bulk heterojunctions based on acceptor-donor-acceptor (A-D-A) nonfullerene acceptors (NFAs) remains unclear. Herein, we study the hole-transfer process between copolymer donor J91 and five A-D-A NFAs with different highest occupied molecular orbital energy offsets (ΔE_H) (0.05-0.42 eV) via ultrafast optical spectroscopies. Transient absorption spectra reveal a rapid hole-transfer rate with small ΔE_H, suggesting that a large energy offset is not required to overcome the exciton binding energy. Capacitance-frequency spectra and time-resolved photoluminescence spectra confirm the delocalization of an A-D-A-structured acceptor exciton with weak binding energy. Relative to the hole-transfer rate, hole-transfer efficiency is the key factor affecting device performance. We propose that holes primarily stem from weakly bound acceptor exciton dissociation, revealing a new insight into the hole-transfer process in A-D-A NFA-based OSCs.