ns² Electron (Bi³⁺ and Sb³⁺) Doping in Lead-Free Metal Halide Perovskite Derivatives

Abstract

Bi³⁺ and Sb³⁺ doping (and codoping with lanthanides) in Cs₂SnCl₆ vacancy ordered perovskites and Cs₂MInCl₆ (M = Na, K, Ag) double perovskites has been shown to open up new opportunities for solid state lighting. Bi³⁺ and Sb³⁺ with ns² outer electronic configuration can tailor both optical absorption and emission properties for phosphor-converted light emitting diode (pc-LEDs) applications. Therefore, the s-electron dopants (Bi³⁺ and Sb³⁺) act as both sensitizers and emitters. This is because the dopant s-electrons contribute near the band edges of the host, unlike the cases of d- and f-electron dopants. Consequently, Bi³⁺ doping can also act as a sensitizer for lanthanide luminescence in systems like Bi³⁺-Ln³⁺ codoped Cs₂AgInCl₆, where Ln = Er, Yb, Tb. In this perspective, we provide insights on the tailoring of electronic and optical properties by ns² electron doping. These insights are then connected to the rational design of hosts, dopants, and codopants, for their potential applications. Finally, we discuss challenges and opportunities for future research.