Optimizing Substrate Chemistry and Perovskite Composition for Reproducible Manufacturing of Efficient and Stable Perovskite Solar Cells

Perovskite-silicon tandems a realistic pathway to efficiencies above 32% and a certified record power conversion efficiency (PCE) of 29.5%, which makes them a promising technology for solar cell applications. Two key challenges for commercialization of perovskite-based tandems are long-term stability and tuning perovskite compositions for different substrate surface chemistries. Here we address how sensitive the solar cell stability is to small fluctuations in perovskite stoichiometry and demonstrate how vapor processing techniques can improve perovskite growth on different surfaces.<br/><br/>We find that perovskite film composition is strongly influenced by the underlying surface. We observe clear trends in X-ray diffraction (XRD) peak position and intensity shifts depending on the underlying surface chemistry. Additionally, we show that the same perovskite deposition on different organic films can lead to similar compositional fluctuations when comparing X-ray fluorescence (XRF) measurements. We discuss how XRD and XRF measurements can be used to determine which perovskite phase is being formed and suggest ways to mitigate detrimental phase formation.<br/><br/>Stoichiometry plays a large role in determining perovskite material stability. Known compositions have a tendency to be photolyzed by blue light and is shown to be one of the main contributing factors to photodegradation in perovskite solar cells. We find spectral illumination d to play a significant role in accelerating light induced degradation. We show a strong correlation between stoichiometry in the initial perovskite film and its rate of degradation under accelerated blue-light photostability testing. We address this issue by tuning our substrate chemistry and the chemistry of our vapor process in order to drastically improve the photostability of perovskite films.<br/><br/>Combining learnings from substrate chemistry studies and photostability studies, we demonstrate scalably deposited solar cells with 20% efficiency and 1000 hours of photostability. It’s likely that we will see record efficiencies upwards of 30% and lifetimes suitable for perovskite solar cell commercialization in the near future.