Cs₄PbBr₆/CsPbBr₃ Perovskite Composites with Near-Unity Luminescence Quantum Yield: Large-Scale Synthesis, Luminescence and Formation Mechanism, and White Light-Emitting Diode Application

Abstract

All-inorganic perovskites have emerged as a new class of phosphor materials owing to their outstanding optical properties. Zero-dimensional inorganic perovskites, in particular the CsPbBr-related systems, are inspiring intensive research owing to the high photoluminescence quantum yield (PLQY) and good stability. However, synthesizing such perovskites with high PLQYs through an environment-friendly, cost-effective, scalable, and high-yield approach remains challenging, and their luminescence mechanisms has been elusive. Here, we report a simple, scalable, room-temperature self-assembly strategy for the synthesis of CsPbBr/CsPbBr perovskite composites with near-unity PLQY (95%), high product yield (71%), and good stability using low-cost, low-toxicity chemicals as precursors. A broad range of experimental and theoretical characterizations suggest that the high-efficiency PL originates from CsPbBr nanocrystals well passivated by the zero-dimensional CsPbBr matrix that forms based on a dissolution-crystallization process. These findings underscore the importance in accurately identifying the phase purity of zero-dimensional perovskites by synchrotron X-ray technique to gain deep insights into the structure-property relationship. Additionally, we demonstrate that green-emitting CsPbBr/CsPbBr, combined with red-emitting KSiF:Mn, can be used for the construction of WLEDs. Our work may pave the way for the use of such composite perovskites as highly luminescent emitters in various applications such as lighting, displays, and other optoelectronic and photonic devices.

Optical Characterization of Cesium Lead Bromide Perovskites

“…The data are reported in Table 1 The onset of the absorption at 2.35 eV is apparently in contrast with the 3.3 eV band gap [39] expected for the presence of Cs 4 PbBr 6 phase (3:1 and 4:1 samples). However, it has been showed that CsPbBr 3 inclusion in Cs 4 PbBr 6 crystals, even at a very low weight ratio, can generate components in the visible absorption spectra in addition to the UV absorption band characteristic of the Cs 4 PbBr 6 phase [40]. Therefore, the absorptions of both phases are present in the spectra of all samples with different contributions: the Cs 4 PbBr 6 increases from 1:1 to 4:1 samples while the other decreases.…”

Single‐Solvent, Ligand‐Free, Gram‐Scale Synthesis of Cs4PbBr6 Perovskite Solids with Robust Green Photoluminescence

“…[29][30][31][32][33][34][35][36] Based on their stability advantage, Cs 4 PbBr 6 have been utilized as matrices to enhance the stability of CsPbBr 3 QDs. [32][33][34][35][36][37] So far, Cs 4 PbBr 6 perovskite materials with green luminescence have also been reported by several groups. [29][30][31] It has been revealed that the green luminescence of these Cs 4 PbBr 6 perovskite materials is irrespective of the particle sizes and morphologies although their luminescent mechanism is still uncertain.…”

“…Recently, as one of promising alternatives to CsPbBr 3 QDs, Cs 4 PbBr 6 perovskite solids with robust green emission have attracted enormous attention due to their stability under ambient condition . Based on their stability advantage, Cs 4 PbBr 6 have been utilized as matrices to enhance the stability of CsPbBr 3 QDs . So far, Cs 4 PbBr 6 perovskite materials with green luminescence have also been reported by several groups .…”

Photoluminescence Mechanisms of All‐Inorganic Cesium Lead Bromide Perovskites Revealed by Single Particle Spectroscopy

“…Due to the structure of electronically isolated [PbBr 6 ] 4− , the first absorption onsets of Cs 4 PbBr 6 NCs with different sizes were found to be located at ∼315 nm . The large direct bandgap of about 3.99 eV suggests that the band‐edge emission of Cs 4 PbBr 6 is expected to occur in the ultraviolet range (Figure a) . However, there are several reports on observation of green PL emission from pure Cs 4 PbBr 6 NCs .…”

“…[47a] The large direct bandgap of about 3.99 eV suggests that the band-edge emission of Cs 4 PbBr 6 is expected to occur in the ultraviolet range (Figure 6a). [10,48] However, there are several reports on observation of green PL emission from pure Cs 4 PbBr 6 NCs. [49] Possible PL mechanisms include the intrinsic emission of Cs 4 PbBr 6 and emission from the [43] Copyright 2017, American Physical Society.…”