Scalable perovskite coating via anti-solvent-free Lewis acid–base adduct engineering for efficient perovskite solar modules†
High-quality large-area perovskite films are realized by an anti-solvent-free adduct approach using 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) as a Lewis base additive. Perovskite crystallization kinetics was found to depend on the latent heat of vaporization, associated with vapor pressure, and donor number of the Lewis base under force convection in air-knife-assisted D-bar coating. The conventionally used dimethyl sulfoxide (DMSO) or N-methyl-2-pyrrolidone (NMP) Lewis base is inappropriate for high-quality perovskite films because of rapid co-evaporation with solvents by argon gas blowing generated under 1.5 MPa, while the DMPU-containing precursor solution induces the formation of a stable adduct intermediate in the as-deposited film due to the low vapor pressure and high donor number of DMPU. Upon addition of DMPU into the precursor solution, the concentration of DMPU is found to affect the morphology and photo-excited carrier lifetime of the resulting perovskite film. A piece of the (FAPbI3)0.95(CsPbBr3)0.05 perovskite film coated on a 4.8 × 9.6 cm2-substrate was used for testing the photovoltaic performance, where the power conversion efficiency (PCE) significantly improved from 3.21% to 20.08% (best PCE is 20.56%) when 0.5 M DMPU (with respect to 1 M of perovskite) was added into the precursor solution. A monolithic perovskite solar module with an active area of 19.69 cm2, employing the perovskite film formed from the 0.5 M DMPU-containing solution, demonstrates a PCE of 17.94%.