High-efficiency deep-red quantum-dot light-emitting diodes with type-II CdSe/CdTe core/shell quantum dots as emissive layers

Abstract

We report a type of highly efficient deep-red light-emitting diode based on type-II CdTe/CdSe core/shell quantum dots (QDs). High-quality CdTe/CdSe core/shell QDs with three different photoluminescence emissions peaked at 642, 664 and 689 nm are, respectively, synthesized through a green process. Correspondingly, three devices employing QDs with different PL peaks show the maximum external quantum efficiency (EQE) of 5.24%, 5.74% and 6.19% with a low turn-on voltage of about 1.8 V, respectively. Interestingly, EQE is kept above 5% in a certain range of luminance (from 10¹ to 10³ cd m⁻²). To our knowledge, this is the first report that uses type-II core/shell QDs as deep-red emitters and these results may offer a practicable reference for applications that require a high efficiency deep-red illuminant.