Acceptor Heterojunction Engineering toward Enhanced Spontaneously Formed Photo-Charges for High-Performance Organic Solar Cells

Utilizing spontaneously formed photocharges (SPs) in Y-series acceptors represents a promising strategy to narrow the efficiency gap between organic solar cells (OSCs) and their inorganic counterparts. However, the practical application of SPs remains constrained by insufficient generation and severe recombination, leading to considerable current density loss (ΔJ). Herein, we introduce a strategy of constructing acceptor heterojunctions, which mitigates losses by effectively reversing the back transition from free carriers to excitons and suppresses their decay to the ground state. As a representative demonstration, incorporating the highly miscible and cascade-energy-aligned acceptor L8-BO into the PM6:BTP-eC9 blend reduces ΔJ from 3.8 mA cm–2 to 3.2 mA cm–2 and enhances the power conversion efficiency from 18.7% to 19.2%. Furthermore, extending this SP optimization strategy to semitransparent OSCs along with tailored optical engineering elevates the light utilization efficiency from 4.19% to 4.60%. This work advances organic photovoltaics toward inorganic-like charge generation mechanisms.