Nonequilibrium site distribution governs charge-transfer electroluminescence at disordered organic heterointerfaces

Significance Semiconducting polymers and small molecules have promising applications in organic optoelectronic devices, such as solar cells, which typically consist of a disordered mixture of donor and acceptor materials. The performance of these devices is determined by the properties of the donor/acceptor interface. While the donor/acceptor interface is often studied by operating the solar cell device as a light-emitting diode, resulting in charge-transfer electroluminescence, the currently prevailing description of electroluminescence is not quantitative and is often inconsistent with experiments. We present an experimentally verified and quantitative model of charge-transfer electroluminescence at donor/acceptor interfaces that reconciles the inconsistencies present in the literature. Our model simultaneously and quantitatively accounts for energetic disorder and molecular vibrations governing charge transport and luminescence in organic semiconductors.