Effect of wettability of substrate on metal halide perovskite growth

Highlights: :• Effect of wettability of substrate on grain size of perovskite layer is studied. • Hydrophobic recovery after UV exposure used to vary wetting properties. • Wetting properties are not the main contributor to grain size of perovskite. In the last decade, inorganic–organic hybrid perovskites have demonstrated a dramatic increase in photoconversion efficiency by engineering the perovskite composition, as well as adjusting the properties of the charge transporting materials. The nucleation and growth of the perovskite layer are governed by the surface properties of the substrate and depend on its wetting properties defined by the roughness and the species adsorbed. Fixing all fabrication conditions of a PSC but only changing the wettability of the substrate is practically difficult because varying the surface hydrophilicity can contribute side effects such as chemical identity change or adsorption of new species on the surface. Herein, we studied a double-layered TiO₂/SnO₂ ETL for perovskite deposition and we changed the hydrophilicity of the samples using hydrophobic recovery after UV exposure. Thus, the effect of wettability of the substrate on nucleation and growth of the perovskite layer was elucidated under minimized interference. It was found that the influence of the wetting properties of the substrate on the growth of perovskite can be exaggerated in the literature since the increase in the grain size of the perovskite layer is just 14% bigger if the water contact angle of the substrate increases from 3° to 72°.