Device Physics in Organic Solar Cells and Drift-Diffusion Simulations

Organic solar cell (OSC) devices have recently exceeded power conversion efficiencies (PCEs) of 17% in single-junction cells (Lin et al., 2019, 2020; Cui et al., 2020; and Liu et al., 2020a, 2020b) and a tandem device using nonfullerene acceptors (NFAs) (Meng et al., 2018). The device performances are still below the predicted efficiency limit of 20% and 25% for single-junction and tandem cells, respectively (Firdaus et al., 2019). Improving OSC device performance further requires a detailed understanding of the underlying physical mechanisms and processes that make the device work, as well as those that lead to performance losses so that materials and device architectures can be further improved. Modeling can fulfill several tasks which range from theoretical discussions of physical mechanisms to the assistance in the interpretation of experiments. Unfolding the physics of these devices to create predictive physical models has been a challenging task due to the complexity of the employed materials and the device physics mechanisms.