Unfolding the Influence of Metal Doping on Properties of CsPbI3 Perovskite

Abstract Low‐temperature α‐phase stabilization using HI or zwitterions in cesium lead iodide (CsPbI 3 ) endures the metastable phase properties but is thermally unstable. Doping with a small amount of heterovalent metals (i.e., Bi 3+ , Sb 3+ ) in CsPbI 3 has been assumed to stabilize the α‐phase, while here this assumption is challenged. It is demonstrated that heterovalent metal ion doping stabilizes β‐CsPbI 3 at low temperatures without replacing the Pb 2+ cations, while divalent cations (i.e., Ba 2+ , Sr 2+ , and Sn 2+ ) doping stabilizes the α‐CsPbI 3 by replacing the Pb 2+ cations. This finding is demonstrated by both theoretical and experimental results. It is also found that the divalent cations stabilize α‐CsPbI 3 films, making thermally stable at high temperatures, whereas heterovalent metal‐doping stabilizes β‐CsPbI 3 films, making metastable. The doping influence on crystal grains and the chemical composition of thin films is discussed. In particular, the charge dissociation kinetics for the Sr doped thin film are much enhanced than α‐CsPbI 3 and Ba doped thin films, also the initial results of the fabricated perovskite red‐light‐emmiting diode suggests that the Sr‐doped thin films would be more suitable for the device fabrication. These findings will guide a way for further development in thermally and air‐stable optoelectronic devices.