High-Performance Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors Enabled by Asymmetric Cores with Enhanced Noncovalent Intramolecular Interactions

Nonfullerene acceptors (MQ3, MQ5, MQ6) are synthesized using asymmetric and symmetric ladder-type heteroheptacene cores with selenophene heterocycles. Although MQ3 and MQ5 are constructed with the same number of selenophene heterocycles, the heteroheptacene core of MQ5 is end-capped with selenophene rings while that of MQ3 is flanked with thiophene rings. With the enhanced noncovalent interaction of O center dot center dot center dot Se compared to that of O center dot center dot center dot S, MQ5 shows a bathochromically shifted absorption band and greatly improved carrier transport, leading to a higher power conversion efficiency (PCE) of 15.64% compared to MQ3, which shows a PCE of 13.51%. Based on the asymmetric heteroheptacene core, MQ6 shows an improved carrier transport induced by the reduced pi-pi stacking distance, related with the increased dipole moment in comparison with the nonfullerene acceptors based on symmetric cores. MQ6 exhibits a PCE of 16.39% with a V-OC of 0.88 V, a FF of 75.66%, and a J(SC) of 24.62 mA cm(-2).

Automated summary

By utilizing different arrangements of selenophene heterocycles, the photovoltaic performance of various nonfullerene acceptors can be improved, resulting in increased efficiency.