Abstract
We report our results of developing perovskite thin films with high coverage, improved uniformity and preserved crystalline continuity in a single pass deposition. This approach, inspired by the natural phenomena of tears of wine, works by regulating the hydrodynamics of the material comprising of droplets during spray-pyrolysis. In contrast to conventional spray-pyrolysis where droplets dry independently and form a rough morphology, the use of binary solvent system creates localized surface tension gradients that initiate Marangoni flows, thus directing the incoming droplets to spontaneously undergo coalescing, merging and spreading into a continuous wet films before drying. By systematically exploring the dynamics of spreading and drying, we achieve spray-coated perovskite photovoltaics with power conversion efficiency of 14.2%, a near two-fold improvement than that of the spray-pyrolysis counterpart. Of particular significance is the fact that the single pass deposition technique unveils novel inroads in efficient management of lead consumption during deposition.