Carrier Mobility Enhancement in (121)-Oriented CsPbBr₃ Perovskite Films Induced by the Microstructure Tailoring of PbBr₂ Precursor Films

It is important to prepare preferentially oriented films to enhance charge carrier transport in the optoelectronic device applications. For the promising optoelectronic material of CsPbBr3, obtaining its thin films with preferred crystal orientation is highly desirable yet challenging. Herein, (121)-oriented CsPbBr3 perovskite films were successfully obtained by using HBr as the additive for PbBr2 precursor solution in the two-step solution method. Detailed investigations indicate that microstructure tailoring of PbBr2 films via HBr additives plays a crucial role in achieving (121)-oriented CsPbBr3 films. Theoretical calculations and experimental measurements demonstrate high carrier mobility in (121)-oriented CsPbBr3 films, which accords well with photovoltaic tests that the (121)-oriented CsPbBr3 film shows short-circuit photocurrent density as much as 1.68 times than the (101)-oriented one. In comparison with the (101)-oriented CsPbBr3 solar cell, the champion power conversion efficiency of the (121)-oriented CsPbBr3 solar cell increases from 2.56 to 6.91% owing possibly to its higher coverage and carrier mobility. This work not only develops a pathway to prepare compact (121)-oriented CsPbBr3 films but also highlights the importance of crystal orientation engineering in perovskite films for high-performance optoelectronic devices.