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• The PL properties of Cs 4 PbBr 6 /CsPbBr 3 have been found to be similar to those of CsPbBr 3 , and extensive characterization and stability show that the luminescence is likely to originate from CsPbBr 3 inclusions. • Temperature-dependent photoluminescent behaviors of the bulk crystals are studied in detail with high binding energy and phonon energy. • The performance of WLED based on Cs 4 PbBr 6 /CsPbBr 3 bulk crystals are measured with luminous efficiency of 64.56 lm/W and cover 128.66% color gamut of the NTSC at 20 mA. The zero-dimensional perovskite composite Cs 4 PbBr 6 /CsPbBr 3 has attracted significant attention for its remarkable photoluminescence (PL), which remains highly effective even in solid state. This work presents a detailed analysis of the steady-state and time-resolved PL (TRPL) behavior of millimeter-scale Cs 4 PbBr 6 /CsPbBr 3 crystals over a temperature range of 80 to 360 K, which covers exciton binding energy, phonon energy, and PL peak energy shifting with increasing temperature. According to the results, Cs 4 PbBr 6 /CsPbBr 3 exhibits high exciton binding energy and phonon energy, with calculated values of 358.7 and 94.8 meV, respectively. Specifically, when the temperature is below ∼235 K, thermal expansion dominates to influence the TRPL and peak energy, whereas electron-phonon interaction becomes the dominant factor as temperature rises from 235 to 325 K. It is found that Cs 4 PbBr 6 /CsPbBr 3 has a PL behavior similar to CsPbBr 3 , and characterization and TRPL results demonstrate that nanometer-scale CsPbBr 3 crystals embed in the Cs 4 PbBr 6 bulk matrix. Meanwhile, a white light-emitting diode (WLED) device based on Cs 4 PbBr 6 /CsPbBr 3 with luminous efficiency of 64.56 lm/W is fabricated, and its color coordinate is measured as (0.34, 0.31) under 20 mA, which is in close proximity to the standard white color coordinate. Moreover, the color gamut of the device is measured as 128.66% of the National Television Systems Committee (NTSC). The WLED electroluminescence (EL) spectra show high Correlated Color Temperature (CCT) stability for the working current varying from 5 to 100 mA, and after continuous operation for 12 h, the EL intensity decreases and stabilizes at ∼70% of the initial EL intensity. These findings suggest that Cs 4 PbBr 6 /CsPbBr 3 crystals are a promising candidate for WLEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

We show here the first colloidal synthesis of double perovskite Cs2AgInCl6nanocrystals (NCs) with a control over their size distribution. In our approach, metal carboxylate precursors and ligands (oleylamine and oleic acid) are dissolved in diphenyl ether and reacted at 105 °C with benzoyl chloride. The resulting Cs2AgInCl6NCs exhibit the expected double perovskite crystal structure, are stable under air, and show a broad spectrum white photoluminescence (PL) with quantum yield of ∼1.6 ± 1%. The optical properties of these NCs were improved by synthesizing Mn-doped Cs2AgInCl6NCs through the simple addition of Mn-acetate to the reaction mixture. The NC products were characterized by the same double perovskite crystal structure, and Mn doping levels up to 1.5%, as confirmed by elemental analyses. The effective incorporation of Mn ions inside Cs2AgInCl6NCs was also proved by means of electron spin resonance spectroscopy. A bright orange emission characterized our Mn-doped Cs2AgInCl6NCs with a PL quantum yield as high as ∼16 ± 4%.