13.4 % Efficiency from All‐Small‐Molecule Organic Solar Cells Based on a Crystalline Donor with Chlorine and Trialkylsilyl Substitutions
Wenyan Su, Yang Wang, Zhihong Yin, Qunping Fan, Xia Guo, Liyang Yu, Yuxiang Li, Lintao Hou, Maojie Zhang, Qiang Peng, Yongfang Li, Ergang Wang
Abstract
Abstract How to simultaneously achieve both high open‐circuit voltage ( V oc ) and high short‐circuit current density ( J sc ) is a big challenge for realising high power conversion efficiency (PCE) in all‐small‐molecule organic solar cells (all‐SM OSCs). Herein, a novel small molecule (SM)‐donor, namely FYSM−SiCl, with trialkylsilyl and chlorine substitutions was designed and synthesized. Compared to the original SM‐donor FYSM−H, FYSM−Si with trialkylsilyl substitution showed a decreased crystallinity and lower highest occupied molecular orbital (HOMO) level, while FYSM−SiCl had an improved crystallinity, more ordered packing arrangement, significantly lower HOMO level, and predominant “face‐on” orientation. Matched with a SM‐acceptor Y6, the FYSM−SiCl‐based all‐SM OSCs exhibited both high V oc of 0.85 V and high J sc of 23.7 mA cm −2 , which is rare for all‐SM OSCs and could be attributed to the low HOMO level of FYSM−SiCl donor and the delicate balance between high crystallinity and suitable blend morphology. As a result, FYSM−SiCl achieved a high PCE of 13.4 % in all‐SM OSCs, which was much higher than those of the FYSM−H‐ (10.9 %) and FYSM−Si‐based devices (12.2 %). This work demonstrated a promising method for the design of efficient SM‐donors by a side‐chain engineering strategy via the introduction of trialkylsilyl and chlorine substitutions.