Decreasing exciton dissociation rates for reduced voltage losses in organic solar cells

Enhancing the device electroluminescence quantum efficiency ( EQE EL ) is a critical factor in mitigating non-radiative voltage losses ( V NR ) and further improving the performance of organic solar cells (OSCs). While the common understanding attributes EQE EL in OSCs to the dynamics of charge transfer (CT) states, persistent efforts to manipulate these decay dynamics have yielded limited results, with the EQE EL of high-efficiency OSCs typically remaining below 10 −2 %. This value is considerably lower than that observed in high efficiency inorganic photovoltaic devices. Here, we report that EQE EL is also influenced by the dissociation rate constant of singlet states ( k DS ). Importantly, in contrast to the traditional belief that advocates maximizing k DS for superior photovoltaic quantum efficiency ( EQE PV ), a controlled reduction in k DS is shown to enhance EQE EL without compromising EQE PV . Consequently, a promising experimental approach to address the V NR challenge is proposed, resulting in a significant improvement in the performance of OSCs.