Interface engineering by ALD in organo-metal halide perovskite solar cells: Reflections on the state-of-the art and perspectives

Over a relatively short period of about ten years, organo-metal halide perovskite solar cells have gained a widespread attention in the photovoltaic community, with a current record efficiency of over 25%. This accomplishment is the result of both fundamental understanding of the perovskite absorber itself (e.g. crystal growth, chemical composition and opto-electronic properties) and improved design and engineering of the device architecture. In this respect, the adoption of atomic layer deposition has been particularly alluring, specifically for the design and engineering of charge transport and passivation layers. In this perspective I reflect on the state-of-the art of ALD processing for perovskite solar cells and on the opportunities and challenges yet to be met.