Red–NIR Luminescence in Rare-Earth and Manganese Ions Codoped Cs4CdBi2Cl12 Vacancy-Ordered Quadruple Perovskites

Combining rare-earth ions (RE3+) in halide perovskites is a hopeful strategy to produce interesting optical properties in visible and near-infrared (NIR) regions. Here, RE3+ (RE: Nd, Ho, Er, Tm) ions are successfully introduced into Cs4Cd1–wMnwBi2Cl12 (0 ≤ w ≤ 1) vacancy-ordered quadruple perovskites through a facile hydrothermal method. In addition to the strong orange-red Mn2+ emission, the as-prepared materials exhibit the effective characteristic emission of RE3+ in the red and NIR regions via constructing a Mn2+ energy bridge. With Mn2+ gradually replacing Cd2+ in Cs4Cd1–wMnwBi2Cl12:RE3+, the photoluminescence (PL) of RE3+ in the red and NIR ranges shows an increasing trend until it reaches the strongest value (w = 1). The energy transfer processes of [BiCl6]3– → Mn2+ → RE3+ are confirmed, and the corresponding mechanism is explored. According to the manipulation of the Mn2+/Cd2+ component, an evolution process from direct to indirect band gaps is verified via a combined experimental–theoretical approach. White light-emitting diodes (LEDs) are fabricated by employing Ho3+-doped Cs4MnBi2Cl12 on near-ultraviolet (n-UV) LED chips, achieving an improved color rendering index (CRI) from 83.3 to 93.0 compared to that of the parent compound. Codoping RE3+ (RE: Nd, Ho, Er, Tm) ions into Cs4MnBi2Cl12 results in an ultrawide emission covering both NIR I and NIR II regions, implying a great potential for NIR detection application.