Significant enhancement of the photovoltaic performance of organic small molecule acceptors via side-chain engineering
Wenyan Su a, Qunping Fan a, Xia Guo*a（国霞）, Juan Chen a, Yan Wang a, Xiaohui Wang b, Ping Dai a, Chennan Ye a, Xiaoguang Bao a, Wei Ma b, Maojie Zhang *a （张茂杰）and Yongfang Li ac
a Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
b State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China c CAS Research/Education Center for Excellence in Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
J. Mater. Chem. A, 2018, 6, 7988--7996
To achieve efficient polymer solar cells (PSCs), it is important to increase the optical absorption coefficient and charge mobility of photovoltaic materials for obtaining a high short-circuit current density (Jsc) and fill factor (FF) in the devices without sacrificing the open-circuit voltage (Voc). Herein, we designed and synthesized two novel narrow bandgap n-type organic semiconductor (n-OS) acceptors named POIT-M and MOIT-M by modifying the side-chains of IT-M from para-hexylphenyl to para-hexyloxylphenyl and then to meta-hexyloxylphenyl. Due to the synergistic effects of introducing oxygen atoms and varying substitution positions on the phenyl side-chains, MOIT-M shows a significantly improved absorption coefficient, stronger intermolecular π–π stacking interaction, increased crystallinity and higher electron mobility in comparison with IT-M and POIT-M, which helps to gain higher Jsc and FF in PSCs. These special features combined with the complementary absorption of the MOIT-M acceptor and wide bandgap polymer PTZ1 donor resulted in a high power conversion efficiency (PCE) of 11.6% with a Voc of 0.96 V, a Jsc of 17.5 mA cm−2 and a FF of 68.8% for the PSCs processed with simple thermal annealing at 120 °C for 10 min, which is one of the highest PCEs reported for additive-free PSCs and significantly higher than those of the PSCs based on PTZ1:IT-M (9.1%) or PTZ1:POIT-M (9.7%). Our results indicate that side-chain engineering is an effective way to further improve the photovoltaic performance of n-OS acceptors in PSCs.
链接：https://pubs.rsc.org/en/Content/ArticleLanding/2018/TA/C8TA01509K#!divAbstract