Mn2+-doping enables improved crystallization of CsPbI3 quantum dots for efficient deep-red light-emitting diodes

Abstract

CsPbI₃ quantum dots (QDs) are attractive candidates for deep-red perovskite light-emitting diodes (PeLEDs) because of their high photoluminescence, good thermal stability, and suitable bandgap. However, the metastable phase of CsPbI₃ QDs hinders the fabrication of efficient deep-red PeLEDs. Herein, Mn²⁺-doped CsPbI₃ QDs were proposed and synthesized via a modified hot injection method. Mn²⁺ with a smaller ionic size leads to lattice shrinkage, which suppressed the distortion of [PbI₆]⁴⁻ and thus polished the CsPbI₃ crystallization. Target deep-red CsPb_1-xMn_xI₃ QDs were endowed with improved photoluminescence quantum yield (PLQY), prolonged fluorescence lifetime, and reduced defect state density. Typically, CsPb_0.977Mn_0.023I₃ QDs achieved the highest PLQY of 58% at 681 nm with Commission International de I’Eclairage coordinates of (0.72, 0.28). Consequently, PeLEDs based on CsPb_0.977Mn_0.023I₃ QDs exhibited a maximum external quantum efficiency of 22.76% (684 nm) and excellent spectrum stability, which is an advanced level among deep-red PeLEDs.