Controlled Growth of CH₃ NH₃ PbI₃ Using a Dynamically Dispensed Spin-Coating Method: Improving Efficiency with a...

It is commonly believed that excess PbI₂ has beneficial effects for perovskite solar cells owing to the modification of charge-transport behavior at interfaces, by surface passivation and by blocking electron-hole recombination. Here, we introduce a dynamically dispensed spin-coating technique in a two-step deposition to form a perovskite layer with controllable quantities of crystalline PbI₂ . Using this technique, the concentration of CH₃ NH₃ I solution is kept constant at the reaction interface, ensuring smooth growth of films. By changing the spinning rate during the reaction, the PbI₂ conversion ratio and perovskite cuboid size can be optimized, resulting in a power conversion efficiency improvement over control devices. This dynamically dispensed technique represents a repeatable method for compositional control in perovskite solar cells and improves our understanding of how a PbI₂ blocking layer improves the performance of perovskite solar cells.