Highly efficient Cu-In-Zn-S/ZnS/PVP composites based white light-emitting diodes by surface modulation

Abstract

Understanding the surface characteristic-optical property relationship of Cu-In-Zn-S (CIZS) quantum dots (QDs) is necessary for tuning the optoelectronic performances, and the photoluminescence quantum yields (PLQYs) of CIZS QDs prepared in aqueous solution are still relative low compared with that of obtained in organic phase, which seriously restricts their applications. Herein, an efficient method was proposed to prepare CIZS/ZnS/PVP composites and their application in white light-emitting diodes (WLEDs) was investigated. CIZS QDs were synthesized through hydrothermal process with the assistance of ionic liquid (IL), which could enhance the PL performance and reduce the reaction time simultaneously. The effects of hydrothermal temperature and time on the phase composition, morphology, and optical properties of CIZS QDs were systematically investigated. The results showed that the BF4− anion played a crucial role in boosting the emission property of CIZS QDs owing to the effective reduction of dangling bonds on the surface of QDs, which induced by the corrosion of F− deriving from the decomposition of BF4−. The surface modulation led to the improvement of PLQY from 6.2% to 8.4%. In addition, the PLQY of QDs was further improved to 31.2% by coating with ZnS shell around CIZS cores. Furthermore, highly luminescent CIZS/ZnS/PVP composites were prepared to eliminate the aggregation-induced fluorescence quenching effect, which was beneficial to the application in WLEDs. Consequently, a WLED achieved the color rending index (CRI) of 87.2, correlated color temperature (CCT) of 4977 K, and luminous efficacy (LE) of 90.11 lm/W by using the orange-yellow CIZS/ZnS/PVP composites and green Lu3Al5O12:Ce3+ phosphors as the color conversion layer, suggesting the potential for solid state lighting application.