Slot-die coating of formamidinium-cesium mixed halide perovskites in ambient conditions with FAAc additive

Continuous pin-hole free FA0.78Cs0.22Pb(I0.85Br0.15)3 films are deposited by gas-assisted slot-die printing under ambient conditions using DMF/DMSO based ink containing Formamdinium Acetate additive. Using a binary solvent mixture of DMF and DMSO is effective in eliminating the non-perovskite phase that occurs when DMF alone is used. Print-speed, gas flow rate and chuck temperature are optimized to realize homogeneous films with constant bandgap (1.63 eV) over large substrates (2″ × 4″). The perovskite films prepared using two solvents DMF and DMF: DMSO (9:1) were incorporated in single junction devices. The resulting devices show improved fill factor with improved power conversion efficiency.