Chalcogen-Atom-Annulated Perylene Diimide Trimers for Highly Efficient Nonfullerene Polymer Solar Cells

This communication reports the synthesis of two novel chalcogen-atom-annulated perylene diimide (PDI) trimers with twisted structures, TriPDI-S and TriPDI-Se, for efficient nonfullerene polymer solar cells. TriPDI-Se exhibits more compact molecular arrangement due to the stronger intermolecular interactions induced by the selenium atom. This selenium annulation endows TriPDI-Se with improved absorption and crystallinity in its blend film. The resulting devices exhibit enhanced J_sc of 17.15 mA cm^-2 and fill factor (FF) of 66.8%, which are much higher than those of TriPDI-S devices (J_sc = 16.71 mA cm^-2 ; FF = 63.6%). Although TriPDI-Se exhibits lower-lying energy levels, TriPDI-Se devices still obtain a higher V_oc of 0.77 V compared to TriPDI-S devices (V_oc = 0.74 V), which is mainly originated from the reduced recombination in the related devices. Finally, the power conversion efficiency is significantly elevated from 7.86% for TriPDI-S devices to 8.82% for TriPDI-Se devices.