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.