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  • 09월 23일 17시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능

제126회 대한화학회 학술발표회 및 총회 Ligand engineered bandgap stability in mixed-halide perovskite nanocrystals light-emitting diodes

2020년 9월 3일 14시 49분 52초
MAT3-2 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
화 15시 : 20분
Materials Chemistry - Recent Trend in Next-Generation Optoelectronics
저자 및
Bo Ram Lee
Department of Physics, Pukyong National University, Korea
Lead halide perovskites are promising semiconductors for light-emitting applications, owing to their bright, bandgap tuneable and high colour purity luminescence. Close to unity photoluminescence quantum yields have been achieved for perovskite nanocrystals across a broad range of emission colours, and light emitting diodes with external quantum efficiencies exceeding 20%, which approach commercial OLEDs, have been demonstrated in both the Infrared and green emission channels. However, due to the formation of lower bandgap iodide-rich domains in mixed-halide perovskites, achieving colour-stable and efficient red electroluminescence at the desired wavelength is yet to be realised. Here, we report mixed-halide perovskite nanocrystals passivated with multidentate ligands that suppress halide segregation, under electroluminescent operation. We demonstrate colour-stable red emission centred at 620 nm, with electroluminescence external quantum efficiencies of 20.3% in light emitting diodes. We use Density Functional Theory to model the nature of binding between the ligands and the nanocrystal surface, which we find suppresses iodine Frenkel defect formation, and infer inhibits halide-segregation. Our work exemplifies how the functionality of metal halide perovskites is extremely sensitive to the nature of the (nano)crystalline surface and presents a route for controlling surface defect formation and migration. This is critical for achieving band gap stability for light emission and will also have a far-reaching impact for other optoelectronic applications, such as photovoltaics, where bandgap stability is required.