A Highly Efficient and Stable Blue‐Emitting Cs5Cu3Cl6I2 with a 1D Chain Structure. Issue 37 (6th August 2020) - Li, Jiangwei
Abstract: In the field of photonics, alkali copper(I) halides attract considerable attention as lead‐free emitters. The intrinsic quantum confinement effects originating from low‐dimensional electronic structure lead to high photoluminescence quantum yields (PLQYs). Among them, Cs3 Cu2 I5 is the most promising candidate, satisfying both high PLQY and air stability. In this study, a strategy to explore a new material meeting these requirements through the use of the mixed‐anions of I − and Cl − is proposed. The expectation is maintained that the large difference in ionic radii between them likely results in the formation of a novel compound. Consequently, Cs5 Cu3 Cl6 I2 with a 1D zigzag chain structure is discovered. This material exhibits blue emission (≈462 nm) with a near‐unity quantum yield of 95%. An electronic structure calculation reveals that the localized nature of the valence band maximum is crucial in obtaining efficient self‐trapped exciton emission. Moreover, the iodine‐bridged 1D connectivity significantly enhances the chemical stability of Cs5 Cu3 Cl6 I2, compared with the pure chloride phase. The present findings provide a new perspective for developing air‐stable alkali copper(I) halides with highly efficient luminescence. Abstract : A new Cu‐based emitting material of Cs5 Cu3 Cl6 I2 that exhibits ultrabright blue‐emission with a near‐unity quantum yield of ≈95% and outstanding long‐term air‐stability is reported. The single‐crystal structure determination reveals that the Cs5 Cu3 Cl6 I2 consists of 1D zigzag chains. Theoretical calculations and extensive comparative studies clarify that the localized nature of the valence band maximum is essential in obtaining efficient self‐trapped exciton emission.