Efficient Ternary Indoor Organic Photovoltaics with Fullerene Derivative as the Host Acceptor and Nonfullerene Material as the Guest Acceptor

For indoor photovoltaic applications, due to the differences in optoelectronic properties of active materials and carrier transport processes under weak light irradiation compared to those under sunlight, it is necessary to optimize the device, especially the active layer, accordingly. In this work, the nonfullerene acceptor L8-BO was innovatively introduced into the PM6:PC71BM heterojunction to construct a ternary system which is specially designed for the indoor photovoltaic device. We compared the parameters of a ternary device with two binary devices (based on PM6:PC71BM and PM6:L8-BO, respectively) under the conditions of sunlight and indoor light illumination and analyzed the mechanism of improving device performance from the aspects of the photophysical properties of the materials, the transport and recombination processes of carriers in the device, and the morphology of the active layer. By optimizing the ratio of the two acceptors, we combined the advantages of the fullerene acceptor and the nonfullerene acceptor to prepare a photovoltaic device that is more suitable for low light intensity and commonly used indoor light source spectra. Its efficiency under 1000 Lux illumination reached 24.21%, which is significantly higher than the corresponding two types of binary devices.