Double Asymmetric Core Optimizes Crystal Packing to Enable Selenophene‐based Acceptor with Over 18 % Efficiency in Binary Organic Solar Cells

Abstract

AbstractSide‐chain tailoring is a promising method to optimize the performance of organic solar cells (OSCs). However, asymmetric alkyl chain‐based small molecular acceptors (SMAs) are still difficult to afford. Herein, we adopted a novel asymmetricn‐nonyl/undecyl substitution strategy and synthesized two A‐D1A′D2‐A double asymmetric isomeric SMAs with asymmetric selenophene‐based central core for OSCs. Crystallographic analysis indicates thatAYT9Se11‐Clforms a more compact and order intermolecular packing compared toAYT11Se9‐Cl, which contributed to higher electron mobility in neatAYT9Se11‐Clfilm. Moreover, thePM6 : AYT9Se11‐Clblend film shows a better morphology with appropriate phase separation and distinct face‐on orientation thanPM6 : AYT11Se9‐Cl. The OSCs withPM6 : AYT9Se11‐Clobtain a superior PCE of 18.12 % compared toPM6 : AYT11Se9‐Cl(17.52 %), which is the best efficiency for the selenium‐incorporated SMAs in binary BHJ OSCs. Our findings elucidate that the promising double asymmetric strategy with isomeric alkyl chains precisely modulates the crystal packing and enhances the photovoltaic efficiency of selenophene‐incorporated SMAs.