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.