Efficient Planar-Heterojunction Perovskite Solar Cells Fabricated by High-Throughput Sheath-Gas-Assisted Electrospray

When a perovskite precursor solution is electrosprayed using the conventional method where the nebulization of the solution is primarily governed by electrostatics, its high electrical conductivity tends to cause electrospray instabilities and thus makes high-quality perovskite films very difficult to obtain. Here, we report high-throughput fabrication of efficient perovskite solar cells (PSCs) whose CH₃NH₃PbI_3-xCl_x films are deposited using a sheath-gas-assisted electrospray system. Our system, based on strong pneumatic nebulization as well as high-voltage electrostatic charging of droplets, enables very stable high-flow electrospray of small charged droplets, even for the highly conductive perovskite precursor solution. Consequently, with the control of the drying rate of the droplets deposited on substrates by adjusting the substrate temperature during deposition, crystalline, void-free CH₃NH₃PbI_3-xCl_x films with nearly 100% surface coverage and high thickness uniformity are obtained. Inverted planar-heterojunction PSCs employing these films have a maximum power conversion efficiency of 14.2% with a small standard deviation of 0.9%, comparable to that of the spin-coated device.