Effect of halide-mixing on tolerance factor and charge-carrier dynamics in (CH3NH3PbBr3−xClx) perovskites powders

This work demonstrates a route to making mixed halide perovskite powders at room temperature by the anti-solvent-assisted crystallization method. Although, mixed halide CH 3 NH 3 PbBr 3− x Cl x perovskites have been prepared by different methods, however , to the best of our knowledge the anti-solvent-assisted crystallization method is employed here for the first time to prepare mixed halide CH 3 NH 3 PbBr 3− x Cl x perovskite powders. Solution-processed methyl ammonium lead tribromide CH 3 NH 3 PbBr 3 ( x = 0) and different amounts of chloride (Cl) containing mixed halide perovskites (CH 3 NH 3 PbBr 3− x Cl x ) were prepared for compositions of x = 0.5, 1, 1.25, 1.75. It reveals that bulk CH 3 NH 3 PbBr 3− x Cl x samples are highly crystalline and exists in pure single cubic phase with an increased tolerance factor as compared to pure CH 3 NH 3 PbBr 3 . The CH 3 NH 3 PbBr 3 perovskite has space-group Pm -3 m and a cell parameter of 5.930 Å (volume = 206 Å). The synthesis route adopted here gives access to hybrid perovskites powders with high Cl content and hence enables the band gap to be precisely tuned over a range from 2.26 to 2.49 eV. The powder samples display the subtle shifts in the emission spectra and the photoluminescence kinetics exhibits a decrease in average lifetime by increasing the Cl contents due to the presence of trap states in the structures that encourage non-radiative recombination of charge carrier. Conventionally, the CH 3 NH 3 PbBr 3 -based inverted solar cell architecture is prepared via mixing of the CH 3 NH 3 Br and PbBr 2 precursors. In contrast, herein, the precursor solutions are directly prepared from the CH 3 NH 3 PbBr 3 powder and the active layer of the inverted perovskite solar cells are then spin coated using this solution. The high V oc value of the fabricated solar cells potentially makes it a promising candidate for tandem photovoltaic, photocatalytic water splitting, and semi-transparent photovoltaic applications.