Self-spreading produces highly efficient perovskite solar cells

A facile two-step drop-coating method was used to make FA0.88MA0.12PbIxBr3−x (0 ≤x ≤ 3) perovskite films for the first time. The films formed via a self-spreading process, without the assistance of coating apparatuses, gas blowing, vacuum, or antisolvent. High-quality perovskite films with different bandgaps were made and the photovoltaic performance was investigated. The cells with FA0.88MA0.12PbI2.85Br0.15 offered a champion PCE of 21.08%, which is higher than the PCEs for perovskite solar cells made by other two-step non-spin-coating methods. The FA0.88MA0.12PbBr3 cells gave a champion PCE of 10.86%, which is the highest PCE for FAxMA1−xPbBr3 cells. The drop-coating method enables making perovskite solar cells without complex equipment. “Fully handmade” perovskite solar cells with drop-coated SnO2, drop-coated perovskite, and painted carbon electrode were made in air, giving a PCE of 14.04%.