Highly efficient and stable Cs2TeCl6:Cr3+ perovskite microcrystals for white light emitting diodes

Abstract

Lead-free perovskites have received great attention in white light emitting diodes (WLEDs), displays, X-ray imaging, etc. However, it still remains a challenge to obtain high photoluminescence quantum yield (PLQY) owing to intrinsic defect intolerance. Here, we develop a facile solvothermal method to incorporate various metal ions (M = Cr³⁺, Mn²⁺, Yb³⁺, Eu³⁺, Sm³⁺, Cd³⁺, Bi³⁺, and Ce³⁺) into Cs₂TeCl₆ vacancy-ordered double perovskite microcrystals (MCs). The broadband yellow emission at 590 nm with PLQY of 6.7% was identified in Cs₂TeCl₆ MCs and was significantly boosted after doping with various metal ions. Interestingly, the optimum Cs₂TeCl₆:Cr³⁺ MCs exhibited a highest PLQY of 81.5% and 31 fold photoluminescence (PL) enhancement compared to Cs₂TeCl₆ MCs. Such improvement after doping could be assigned to (i) the radiative recombination rate enhancement induced by octahedral distortion and (ii) decrease in nonradiative recombination rates caused by the decrease in electron–phonon coupling and increase in exciton binding energy. In addition, Cs₂TeCl₆:Cr³⁺ also showed excellent moisture resistance and photo-stability. Thus, WLEDs with high stability and brightness based on the mixture of Cs₂TeCl₆:Cr³⁺ and BaMgAl₁₀O₁₇:Eu²⁺ phosphors were achieved, demonstrating a Commission Internationale de l’Eclairage (CIE) of (0.32, 0.35), high color rendering index (CRI) of 81.3, and correlated color temperature (CCT) of 5826 K. This work will facilitate the development of lead-free perovskites and expand their applications in solid-state lighting.