Revealing the Critical Role of the HOMO Alignment on Maximizing Current Extraction and Suppressing Energy Loss in Organic Solar Cells

Jianyun Zhang; Wenrui Liu; Ming Zhang; Yanfeng Liu; Guanqing Zhou; Shengjie Xu; Fengling Zhang; Haiming Zhu; Feng Liu; Xiaozhang Zhu

doi:10.1016/j.isci.2019.08.038

Revealing the Critical Role of the HOMO Alignment on Maximizing Current Extraction and Suppressing Energy Loss in Organic Solar Cells

iScience. 2019 Sep 27:19:883-893. doi: 10.1016/j.isci.2019.08.038. Epub 2019 Aug 27.

Authors

Jianyun Zhang¹, Wenrui Liu¹, Ming Zhang², Yanfeng Liu³, Guanqing Zhou², Shengjie Xu⁴, Fengling Zhang³, Haiming Zhu⁵, Feng Liu⁶, Xiaozhang Zhu⁷

Affiliations

¹ Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China.
² School of Chemistry and Chemical Engineering, and Center for Advanced Electronic Materials and Devices, Shanghai Jiao Tong University, Shanghai 200240, China.
³ Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-581 83, Sweden.
⁴ Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China. Electronic address: [email protected].
⁵ Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
⁶ School of Chemistry and Chemical Engineering, and Center for Advanced Electronic Materials and Devices, Shanghai Jiao Tong University, Shanghai 200240, China. Electronic address: [email protected].
⁷ Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China. Electronic address: [email protected].

Abstract

For state-of-the-art organic solar cells (OSCs) consisting of a large-bandgap polymer donor and a near-infrared (NIR) molecular acceptor, the control of the HOMO offset is the key to simultaneously achieve small energy loss (E_loss) and high photocurrent. However, the relationship between HOMO offsets and the efficiency for hole separation is quite elusive so far, which requires a comprehensive understanding on how small the driving force can effectively perform the charge separation while obtaining a high photovoltage to ensure high OSC performance. By designing a new family of ZITI-X NIR acceptors (X = S, C, N) with a high structural similarity and matching them with polymer donor J71 forming reduced HOMO offsets, we systematically investigated and established the relationship among the photovoltaic performance, energy loss, and hole-transfer kinetics. We achieved the highest PCE_avgs of 14.05 ± 0.21% in a ternary system (J71:ZITI-C:ZITI-N) that best optimize the balance between driving force and energy loss.

Keywords: Energy Storage; Materials Characterization; Solid State Physics.