Impact of Electrostatic Interaction on Non‐radiative Recombination Energy Losses in Organic Solar Cells Based on Asymmetric Acceptors

Abstract

AbstractReducing non‐radiative recombination energy loss (ΔE3) is one key to boosting the efficiency of organic solar cells. Although the recent studies have indicated that the Y‐series asymmetric acceptors‐based devices featured relatively low ΔE3, the understanding of the energy loss mechanism derived from molecular structure change is still lagging behind. Herein, two asymmetric acceptors named BTP‐Cl and BTP‐2Cl with different terminals were synthesized to make a clear comparative study with the symmetric acceptor BTP‐0Cl. Our results suggest that asymmetric acceptors exhibit a larger difference of electrostatic potential (ESP) in terminals and semi‐molecular dipole moment, which contributes to form a stronger π–π interaction. Besides, the experimental and theoretical studies reveal that a lower ESP‐induced intermolecular interaction can reduce the distribution of PM6 near the interface to enhance the built‐in potential and decrease the charge transfer state ratio for asymmetric acceptors. Therefore, the devices achieve a higher exciton dissociation efficiency and lower ΔE3. This work establishes a structure‐performance relationship and provides a new perspective to understand the state‐of‐the‐art asymmetric acceptors.