Realizing Efficient Emission in Three-Dimensional CsCdCl3 Single Crystals by Introducing Separated Emitting Centers

Hitherto, three-dimensional (3D) perovskite single crystals with a low exciton binding energy generally possess inferior photoluminescence (PL) performance due to the spatially unconfined nature of excitons. In this work, 3D CsCdCl3 single crystals with multiple emissions from self-trapped excitons (STEs) have been developed, which unsurprisingly exhibit a discouraging PL quantum yield (PLQY) of ∼4.8%. To improve the luminescence efficiency, Mn2+ and Sn2+ are introduced into the lattice as dopants, respectively. By embedding Mn2+ ion into CsCdCl3, the long Mn–Mn distance enables the resultant material to produce an intense orange emission (∼100% PLQY) from the d–d orbital transition (4T1–6A1) of Mn2+. Intriguingly, the embedded Sn2+ triggers the formation of Jahn–Teller-like STEs that induces a subsequent deep red emission with a PLQY of ∼28.22%, which is quite high for 3D bulk perovskites. Such a remarkable PL efficiency is attributed to the distinctive bonding mode of CsCdCl3 that encourages the expression of the Sn 5s2 lone pair. Furthermore, a white-light-emitting diode (WLED) is also fabricated with Mn2+-doped CsCdCl3 to show its potential in lighting application. This work paves a new avenue to improve the luminescence performance of bulk 3D perovskite materials.