Spray‐coating is a versatile coating technique that can be used to deposit functional films over large areas at speed. Here, spray‐coating is used to fabricate inverted perovskite solar cell devices in which all of the solution‐processible layers (PEDOT:PSS, perovskite, and PCBM) are deposited by ultrasonic spray‐casting in air. Using such techniques, all‐spray‐cast devices having a champion power conversion efficiency (PCE) of 9.9% are fabricated. Such performance compares favorably with reference devices spin‐cast under a nitrogen atmosphere that has a champion PCE of 12.8%. Losses in device efficiency are ascribed to lower surface coverage and reduced uniformity of the spray‐cast perovskite layer.

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We explore degradation pathways within encapsulated CH 3 NH 3 PbI 3-x Cl x perovskite devices based on the inverted architecture: ITO/PEDOT:PSS/CH 3 NH 3 PbI 3-x Cl x /PC 70 BM/LiF/Al. Devices were subjected to more than 670 h of continuous illumination approximating AM1.5, with a Ts80 lifetime of (280 ± 20) hours determined. Devices stored in the dark underwent a similar drop in efficiency over the same time-period. Using external quantum efficiency, time-resolved photoluminescence, X-ray diffraction, scanning electron microscopy and laser beam induced current mapping, we attribute the primary cause of degradation to reactions with residual moisture trapped in the device, resulting in the decomposition of the perovskite. 36