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High-quality all-inorganic perovskite CsPb(BrxI1-x)3 quantum dots (QDs) with quantum yield of 50% were systematically studied as yellow light convertor for light emitting diodes (LEDs). A novel heat insulation structure was designed for the QD-converted yellow LEDs. In this structure, a silicone layer was set on top of the GaN LED chip to prevent directly heating of the QDs by the LED chip. Then the CsPb(BrxI1-x)3 QDs were filled in the bowl-shaped silicone layer after ultrasonic dispersion treatment. Finally, an Al2O3 passivation layer was grown on the QDs layer by Atomic Layer Disposition at 40 °C. When x = 0.55, highly pure yellow LEDs with an emission peak at ∼570 nm and a full width at half maximum of 25 nm were achieved. The chromaticity coordinates of the QD-converted yellow LEDs (0.4920 ± 0.0017, 0.4988 ± 0.0053) showed almost no variation under driving current from 5 mA to 150 mA. During an operation period of 60 min, the emission wavelength of the yellow LEDs showed no distinct shift. Moreover, the luminous efficiency of the QD-converted yellow LEDs achieved 13.51 l m/W at 6 mA. These results demonstrated that CsPb(BrxI1-x)3 QDs and the heat insulation structure are promising candidate for high purity yellow LEDs.

A GaN/CH3NH3PbBr3 heterojunction was fabricated by depositing a GaN thin layer on a CH3NH3PbBr3 single crystal by plasma enhanced atomic layer deposition. The band alignment of the GaN/CH3NH3PbBr3 heterojunction was studied by x-ray photoelectron spectroscopy. The valance band offset (VBO) is directly determined to be 0.13 ± 0.08 eV. The conduction band offset is deduced from the VBO and the band gaps, which turned out to be 1.39 ± 0.12 eV. Thus, the band alignment of the GaN/CH3NH3PbBr3 heterojunction is determined to be type-I. These results show that GaN is a promising material for carrier confinement in halide perovskite based light emitting devices.