Decoupling the Transparency-Efficiency Trade-Off in Semi-Transparent Organic Solar Cells via Optimized Dual-Channel Photoelectric Conversion

The development of semi-transparent organic solar cells (ST-OSCs) for building-integrated photovoltaics is fundamentally constrained by the inherent trade-off between transparency and efficiency. To achieve a breakthrough, it is imperative to maintain high transparency while mitigating the concomitant efficiency loss in low-donor-content devices. Herein, we address this challenge by implementing a strategy that optimizes dual-channel photoelectric conversion, which synergistically integrates the respective advantages of both the heterojunction (HJ) channel and the spontaneously formed photo-charge (SP) channel. The results reveal that the HJ channel primarily governs hole transport and thus the fill factor, whereas the SP channel is pivotal for charge generation, directly influencing the short-circuit current density. Strategic acceptor selection and dual-additive-assisted morphology control effectively minimize electrical losses from insufficient charge generation and severe recombination, enabling a remarkable power conversion efficiency of 11.3% in PTB7-Th:BTP-eC9 (1:4) devices that outperforms their bulk heterojunction (BHJ) counterparts (10.4%), without losing the high transparency (>65%). The general applicability of this strategy was further validated in PM6:BTP-eC9 (1:3) based ST-OSCs, yielding a competitive light utilization efficiency of 4.67% and demonstrating the generalizability of our approach across different active layer systems. This study reveals the crucial role of dual-channel photoelectric conversion in realizing high-performance ST-OSCs.