DMF-mediated polycrystalline phase transition of Cd-based perovskites: dual-emission tuning for temperature sensing and single-component white LEDs

Abstract

Phase transition dynamics in perovskite polycrystalline materials present intriguing scientific phenomena; yet achieving precise phase selection and synthesis remains a significant challenge. Herein, we demonstrate controlled synthesis of three distinct phases within the Cs–Cd–Cl system through a DMF-mediated co-precipitation method. By systematically varying the volume ratio of DMF to HCL (0, 1, and 1.5), high-purity CsCdCl₃, Cs₃Cd₂Cl₇, and Cs₂CdCl₄ phases were successfully obtained via DMF solvent modulation. By introducing Pb²⁺, the obtained Cd-based perovskites have a high photoluminescence efficiency, demonstrating the cyan-blue emissions centered at 507, 436 and 450 nm, respectively. Notably, Pb²⁺,Mn²⁺ co-doped Cs₃Cd₂Cl₇ exhibits dual-emission peaking at 436 nm and 584 nm, attributed to efficient energy transfer from Pb²⁺ to Mn²⁺, enabling spectral tuning from the blue to the orange band. Interestingly, Cs₃Cd₂Cl₇:1%Pb²⁺,1%Mn²⁺ demonstrates an anomalous anti-thermal quenching behavior suitable for fluorescence intensity ratio (FIR) based temperature sensing, achieving the maximum relative sensitivity (S_r) of 3.40% K⁻¹ (at 298 K) and absolute sensitivity (S_a) of 4.45% K⁻¹. Furthermore, the dual-emission phosphors show the tunable capabilities for fabricating both warm-white and cool-white LEDs. This work proposes a novel strategy for manipulating photoluminescence properties through polycrystalline phase transformation in Cs–Cd–Cl systems, while revealing significant potential in advanced optical thermometry and single-component white-light LED devices.