Stabilizing Perovskite Halide Solar Absorbers through Direct Atomic Layer Deposition of Pinhole-free Oxides

Direct deposition of pinhole-free oxide thin films by atomic layer deposition (ALD) have proven to be an efficacious route to passivation layers and diffusion barriers in many applications. However, perovskite halides absorbers are largely incompatible with the process conditions for conventional atomic layer deposition oxides, namely temperatures greater than 100 degrees C and oxygen sources that include water or ozone. We have identified deposition chemistry based on an anhydrous acetic acid oxygen source which can be applied directly to perovskite halide thin films to produce oxide overlayers (including TiO2) that dramatically stabilize against relative humidity, liquid water, and temperatures up to 250 degrees C.