Measuring the Effects of Slow Electron Transport in Cesium Copper Iodide Light-Emitting Diodes by Pulsed Voltage Operation

The development of direct charge-injection LEDs using self-trapping exciton (STE) materials lags behind. In this work, we fabricated thin-film LEDs using CsCu2I3, a typical STE emitter, with two different electron-transporting layers (ETL), 2,2′,2′′-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) and 1,3,5-tris(3-pyridyl-3-phenyl)benzene (TmPyPB). Using a pulsed applied voltage, we examined the charging and emission mechanisms through time-resolved electroluminescence (TREL) coupled to time-resolved current (TRC) measurements. As revealed by TREL and TRC analysis, slower electron transport in TPBi devices enhances charge balance, thereby boosting luminance and causing a redshift in emission. This study provides considerable insight and is valuable for the further development of lead-free STE LEDs.