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Abstract:

Cesium lead halide perovskite nanocrystals (NCs) have unique optical properties such as high color purity and high photoluminescence (PL) efficiency. However, the external quantum efficiency (EQE) of the corresponding light-emitting diodes (LEDs) is low, primarily as a result of the NC surface defects. Here, we report a method to reduce the surface defects by capping CsPbI₃ NCs with PbS. This passivation significantly enhanced the PL efficiency, reduced the Stokes shift, narrowed the PL bandwidth, and increased the stability of CsPbI₃ NCs. At the same time, CsPbI₃ NC films switched from n-type behavior to nearly ambipolar by PbS capping, which allowed us to fabricate electroluminescence LEDs using p-i-n structures. The thus-fabricated LEDs exhibited dramatically improved storage and operation stability, and an EQE of 11.8%. These results suggest that, with a suitable surface passivation strategy, the perovskite NCs are promising for next-generation LED and display applications.

Abstract:

Lead halide perovskite nanocrystals are currently under intense investigation as components of solution-processed light-emitting devices (LEDs). We demonstrate LEDs based on Ag doped-passivated CsPbI₃ perovskite nanocrystals with external quantum efficiency of 11.2% and an improved stability. Ag and trilayer MoO₃/Au/MoO₃ structure were used as cathode and anode, respectively, which reduce the electron injection barrier and ensure the high transparency and low resistance of the anode. Silver ions diffuse into perovskite film from the Ag electrode, as confirmed by the elemental mapping, the presence of Ag 3d peaks in the X-ray photoelectron spectrum, and the peak shift in the X-ray diffraction patterns of CsPbI₃. In addition to doping, silver ions play the beneficial role of passivating surface defect states of CsPbI₃ nanocrystals, which results in increased photoluminescence quantum yield, elongated emission lifetime, and improved stability of perovskite films.

Abstract:

Inorganic perovskite quantum dots bear many unique properties that make them potential candidates for optoelectronic applications, including color display and lighting. However, the white emission with inorganic perovskite quantum dots has rarely been realized due to the anion-exchange reaction. Here, we proposed a one-pot preparation to fabricate inorganic perovskite quantum dot-based white light-emitting composites by introducing anthracene as a blue emission component. The as-prepared white light-emitting composite exhibited a photoluminescence quantum yield of 41.9%. By combining CsPb(Br/I)₃@anthracene composites with UV light-emitting device (LED) chips, white light-emitting devices with a color rendering index of 90 were realized with tunable color temperature from warm white to cool white. These results can promote the application of inorganic perovskite quantum dots in the field of white LEDs.

Abstract:

The surface organic ligands of the quantum dots (QDs) play important roles in the performance of QD electronic devices. Here, we fabricated low toxic AgIn₅S₈/ZnS QDs light-emitting diodes (QD-LEDs) and greatly enhanced the device efficiency through surface ligand exchange treatments. The oleic acid-capped QDs were replaced with a shorter ligand 1,2-ethanedithiol, which was proved by the Fourier transform infrared spectrum measurement. The treated QD films became more compact with higher film mobility and shorter film photoluminescence lifetime. The more conductive QD films fabricated LEDs showed an external quantum efficiency over 1.52%.