Asymmetric Glycolated Substitution for Enhanced Permittivity and Ecocompatibility of High-Performance Photovoltaic Electron Acceptor

Tengfei Li; Kang Wang; Guilong Cai; Yawen Li; Heng Liu; Yixiao Jia; Zhenzhen Zhang; Xinhui Lu; Ye Yang; Yuze Lin

doi:10.1021/jacsau.1c00306

Asymmetric Glycolated Substitution for Enhanced Permittivity and Ecocompatibility of High-Performance Photovoltaic Electron Acceptor

JACS Au. 2021 Aug 18;1(10):1733-1742. doi: 10.1021/jacsau.1c00306. eCollection 2021 Oct 25.

Authors

Tengfei Li¹, Kang Wang², Guilong Cai³, Yawen Li¹, Heng Liu³, Yixiao Jia¹, Zhenzhen Zhang^{1

4}, Xinhui Lu³, Ye Yang², Yuze Lin^{1

4}

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 State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
³ Department of Physics, The Chinese University of Hong Kong, New Territories 999077, Hong Kong, China.
⁴ University of Chinese Academy of Sciences, Beijing 100049, China.

Abstract

Traditional organic photovoltaic materials exhibit low dielectric constants (ε_r) of 3 to 4, restricting the further enhancement of power conversion efficiencies (PCEs) of organic solar cells (OSCs). Herein we design and synthesize a fused-ring electron acceptor named Y6-4O through introducing an asymmetric highly polarizable oligo(ethylene glycol) side chain onto the pyrrole unit of Y6. Compared with alkylated Y6 (ε_r = 3.36), asymmetric glycolated Y6-4O shows a notably higher ε_r value of 5.13 and better solubility in nonhalogen solvents. Because of the higher ε_r value, the devices based on as-cast PM6:Y6-4O processed using toluene exhibit a higher charge separation yield, slower bimolecular recombination kinetics, and less voltage loss relative to the control devices based on PM6:Y6. Consequently, a high PCE of 15.2% is achieved for PM6:Y6-4O-based devices, whereas the PM6:Y6-based devices show PCEs of only 7.38%. 15.2% is the highest PCE for the as-cast nonhalogenated processed OSC devices, and it is also much higher than the values (<8.5%) reported for OSCs based on high-permittivity (ε_r > 5) organic photovoltaic semiconductors.