Efficient light-emitting diodes based on reverse type-I quantum dots

Reverse type-I core/shell quantum dots (QDs) have attracted much interest owing to their much more tunable emissions as compared with type-I QDs, thus benefiting full color display. However, the choices of the reverse type-I material are quite limited and their photoluminescence quantum yields (QYs) are still low, which restricts their further applications in optoelectronics. Here, we present the synthesis of highly bright CdxZn(1-x)S/CdSe reverse type-II QDs with a wide tunable emission ranging from 450 to 670 nm and a quantum yield of 61% at 638 nm. Two red quantum dot light-emitting diodes based on Cd0.1Zn0.9S/CdSe and CdSe/Cd0.1Zn0.9S have been fabricated to study the influence of energy level alignment on the device performances. The luminance and external quantum efficiency of the Cd0.1Zn0.9S/CdSe device (11412 cd/m(2) and 8.23%) are much higher than that of CdSe/Cd0.1Zn0.9S one, despite its lower PL QY. Evidence shows that the reverse type-I structure benefits the charge injection into the emitting material without overcoming the large physical barrier of the outer shell, thus leading to notable improvements in device performances. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement