Modulating CsPbl3 crystallization by using diammonium agent for efficient solar cells

Abstract Cesium lead triiodide (CsPbI 3 ) perovskite receives tremendous attention for photovoltaic applications, owing to its remarkable thermal stability and optoelectronic properties. However, realizing the CsPbI 3 perovskite with high black‐phase stability and optoelectronic properties remains a significant challenge, which largely affects the photovoltaic performance of perovskite solar cells (PSCs). Herein, aromatic ammonium agents are used to modulate the crystallization of the CsPbI 3 perovskite to improve its black‐phase stability and optoelectronic properties for efficient PSCs. Systemically experimental studies and comprehensively theoretical calculations are performed, which reveal that histammonium dihydrochloride (HACl 2 ) could strongly couple with the perovskite during its crystallization, leading to faster nucleation and slower perovskite growth, and thus modulating the crystallization dynamics of the perovskites. Moreover, the residual diammonium cations (HA 2+ ) distributed at the grain boundaries and on the surface of the perovskites can effectively passivate defects through electrostatic interactions, substantially suppressing trap‐assisted nonradiative recombination, and prompting more matched perovskite surface energetics. Consequently, the photovoltaic performance of CsPbI 3 PSCs is largely improved because of a combination of enhanced crystallinity and optoelectronic properties of the perovskites. This work offers a new avenue to prepare inorganic perovskites with high optoelectronic properties for photovoltaics.