Impact of charge generation and extraction on photovoltaic performances of spin- and blade-as well as spray-coated organic solar cells

Abstract

The fullerene- and nonfullerene-based organic solar cells (OSCs), which are compatible with low-cost solution-coating technologies, have attracted widespread attention in recent years. However, compared to the OSCs by spin-coating, the underlying reasons behind photovoltaic degradation for the OSCs by blade- and spray-coating are rarely investigated, which severely limits the further progress of OSC industrialization. In this work, the JSC difference between fullerene/nonfullerene OSCs by different coating techniques is systematically studied by analyzing the internal quantum efficiency and reconstructing the external quantum efficiency. Moreover, for both the fullerene and nonfullerene systems, the ratio of charge recombination over charge extraction in the blade-coated OSCs is very close to that in the spin-coated devices, whereas there is a clearly larger discrepancy between the spray-coated and the spin-coated ones. In terms of the ultimately achieved power conversion efficiencies, which is mainly related to the solid-state morphologies of active films by different coating techniques, the fullerene system presents better tolerance to fab-scale coating methods than that of the nonfullerene system. The J-V curves calculated by the drift-diffusion equations fit well with the actual J-V curves, verifying the correctness of above analysis and the usefulness of our conclusions. This work demonstrates the causes of performance loss among the spin- and blade- and spray-coated fullerene/nonfullerene OSCs, which provides useful insights for future manufacturing of OSCs.