Revealing Photodegradation Pathways of Organic Solar Cells by Spectrally Resolved Accelerated Lifetime Analysis

Abstract A method for organic solar cell (OSC) stability testing is presented that aims to provide more unique insight into the causes of degradation patterns of OSCs. The method involves using monochromatic light at high irradiation doses to accelerate isolated degradation mechanisms while monitoring the device with a series of in‐situ steady‐state and transient electrical measurements. The experimental results are accompanied by drift‐diffusion simulations to localize degradation pathways. PM6:Y6‐based OSCs are tested, which are known to show a rather broad range of lifetimes as a function of device architecture, material batches, or degradation conditions. The experiments reveal a degradation mechanism that causes an increased trap‐state density inside the PM6:Y6 layer. The transient simulations suggest that these states are formed at or around the interface between the PM6:Y6 and the electron transport layer. Furthermore, the surprisingly dominant impact of the illuminating wavelength on the degradation pattern is evidenced. Lastly, the degradation rate of the devices scales linearly with light intensity, making high intensity and spectrally selective degradation the most promising way to accelerate stability testing for the faster development of stable OSCs.