Steady and transient optical properties of CsPbBr3/Pb3(PO4)2 perovskite quantum dots for white light-emitting diodes

Abstract

Surface passivation has been widely accepted as an effective method to improve the stability and photoluminescence (PL) performance of perovskite quantum dots (QDs). In this paper, we report Pb₃(PO₄)_2-coated CsPbBr₃ QDs as the phosphor materials for white light-emitting diodes. The Pb₃(PO₄)₂ coated layer could effectively improve the stability and optical properties of CsPbBr₃ QDs, including PL intensity, average PL lifetime, and PL quantum yield. Moreover, the temperature-dependent PL spectra of CsPbBr₃ and CsPbBr₃/Pb₃(PO₄)₂ QDs were investigated. It was found that the exciton binding energy and electron–phonon coupling effect of CsPbBr₃/Pb₃(PO₄)₂ QDs was larger than that of uncoated QDs. According to the results of transient absorption (TA), intraband hot-exciton relaxation and exciton recombination can be slowed down when the CsPbBr₃ QDs are coated with Pb₃(PO₄)₂. In addition, white light-emitting diode devices were fabricated by integrating the green CsPbBr₃/Pb₃(PO₄)₂ QDs and red CsPbBr₁I₂/Pb₃(PO₄)₂ QDs on the blue GaN chips. The devices showed stable white light emission with Commission Internationale de L’Eclairage color coordinates of (0.297, 0.333). As indicated by the results, Pb₃(PO₄)_2-coated perovskite QDs could be an ideal down-conversion fluorescent material for white light-emitting diode devices.