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■ 제 목: Interconversion of charge, light and spin in halide perovskites for efficient spin-optoelectronics
■ 연 사: 김영훈 교수 (한양대학교 에너지공학과)
■ 일 시: 2022년 4월 12(화) 오후 4시
■ Host : 조힘찬 교수
■ 참가자 접속정보 (3:50분까지 참가를 부탁드립니다)
■ Abstract :
Efficient interconversion of charge and light in light-emitting diodes (LEDs) is limited by lack of comprehensive materials design strategies both to suppress formation of defects and to enhance charge carrier confinement inside perovskite nanocrystals (PNCs). First, we design a one-dopant alloying strategy that generates smaller, monodisperse colloidal particles (confining e- and h+ and boosting radiative recombination) with fewer surface defects (reducing nonradiative recombination). Doping of larger guanidinium (GA) into formamidinium (FA) lead bromide PNCs yields limited bulk solubility, above which extra GA segregates to the surface and stabilizes the under-coordinated sites. Increasing GA concentration requires higher surface/volume, leading to smaller PNCs for more carrier confinement. Furthermore, colloidal PNCs which decouple the crystallization of perovskites from the film formation achieve high external quantum efficiency (EQE) of 23.26% in a pixel area of 4 mm2, of 22.5% in 102 mm2 and 21.46% in 900mm2.
Second, to overcome the fundamental limitation and expand the possibilities of traditional optoelectronic devices, we employ chiral induced spin selectivity (CISS) to produce spin-polarized carriers and demonstrate a spin-LED that operates at room temperature without magnetic fields or ferromagnetic contacts. The CISS layer consists of self-assembled chiral molecules within a layered perovskite framework and spin-LEDs achieve circularly-polarized electroluminescence at room temperature from PNC emitting layers.