Effects of temperature and coating speed on the morphology of solution-sheared halide perovskite thin-film

Abstract

We have conducted a systematic study of crystallization of perovskite thin-film during solution shearing to elucidate how parameters such as substrate temperature and coating speed influences the crystallinity and morphology of the thin-film. Four distinct phases are identified and a morphology-phase map is constructed. Formation of these phases was attributed to a delicate balance between supersaturation rate and rate of solution supply to the meniscus, which dictated the nucleation and the crystal growth process. An optimal phase window is identified and the photovoltaic device performance with the chosen condition exhibits power conversion efficiency over 15%, which is comparable to a reference device prepared by the conventional spin-coating process. Furthermore, a large area perovskite film of $57 cm^2$ is prepared. Small-area devices from different locations within the large-area film show uniform efficiencies with deviation coefficient of 4.2%, illustrating the high uniformity of thin-film.