Interstitial Mn2+-Driven High-Aspect-Ratio Grain Growth for Low-Trap-Density Microcrystalline Films for Record Efficiency CsPbI2Br Solar Cells

It is imperative to develop a large-aspect-ratio grain-based thin film with low trap density for high-performance inorganic perovskite CsPbI 2 Br solar cells. Herein, by using Mn 2+ ion doping to modulate film growth, we achieved CsPbI 2 Br grains with aspect ratios as high as 8. It is found that Mn 2+ ions insert into the interstices of the CsPbI 2 Br lattice during the growth process, leading to suppressed nucleation and a decreased growth rate. The combination aids in the achievement of larger CsPbI 2 Br crystalline grains for increased J SC values as high as 14.37 mA/cm 2 and FFs as large as 80.0%. Moreover, excess Mn 2+ ions passivate the grain boundary and surface defects, resulting in effectively decreased recombination loss with improved hole extraction efficiency, which enhances the built-in electric field and hence increases V OC to 1.172 V. As a result, the champion device achieves stabilized efficiency as high as 13.47%, improved by 13% compared with only 11.88% for the reference device.