TY - JOUR AB - Methylammonium lead halide perovskites are attracting intense interest as promising materials for next-generation solar cells, but serious issues related to long-term stability need to be addressed. Specifically, perovskite films based on CH3NH3PbI3 undergo fast oxygen- and light-induced degradation. However, the mechanism of such degradation and its relation to particle size and oxygen transport are poorly understood. Here, we report new mechanistic insights through the combined use of isothermal gravimetric analysis, photoluminescence, secondary ion mass spectrometry and ab initio simulation techniques. We find fast oxygen diffusion into CH3NH3PbI3 films is accompanied by superoxide formation, which are critical to degradation by oxygen in the atmosphere.Perovskite films composed of small crystallites show high yields of photo-induced superoxide species and low stability. Ab initio simulations indicate that iodide vacancies are the preferred sites in mediating the photo-induced formation of superoxide species from oxygen. We also show that thin-film passivation with iodide salts can lead to enhanced film stability and thus device stability. The understanding of degradation phenomena gained from this study is important for the future design and optimisation of perovskite solar cells with greater stability. AU - Aristidou,N AU - Haque,S AU - Eames,C AU - Sanchez-Molina,I AU - Bu,X AU - Kosco,J AU - Saiful,Islam M AU - Haque,SA DO - 10.1038/ncomms15218 EP - 10 PY - 2017/// SN - 2041-1723 SP - 1 TI - Fast oxygen diffusion and iodide defects mediate oxygen-induced degradation of perovskite solar cells T2 - Nature Communications UR - http://dx.doi.org/10.1038/ncomms15218 UR - https://www.nature.com/articles/ncomms15218 UR - http://hdl.handle.net/10044/1/44949 VL - 8 ER -