Abstract
A novel cryo-controlled nucleation technique is developed to grow mixed halide perovskite for solar cells (PSCs). The abrupt decrease in the ambient temperature results in a supersaturation condition in the precursor film prepared by the spin coating process, leading to form uniform nucleation sites for subsequent crystal growth. The low temperature ambient retards the pre-mature crystallization of the perovskite film in the early stage before a uniform seed layer is obtained. This film deposition approach ensures excellent uniformity of the nucleation layers and, subsequently, higher quality perovskite films. A power conversion efficiency (PCE) of 21.4 % for the champion PSC can be achieved by the proposed perovskite growth technique.