Efficient quantum-dot light-emitting diodes using ZnS-AgInS2 solid-solution quantum dots in combination with organic charge-transport materials

Abstract

Colloidal quantum dots (QDs), which exhibit highly saturated color emission, are expected to be used as emitting materials in wide-color-gamut displays. However, the development of low-toxicity alternatives is necessary because QDs with high color purity and highly efficient emission contain toxic materials such as Cd and Pb. In this study, QD light-emitting diodes (QD-LEDs) with ZnS-AgInS2 solid-solution nanoparticles [(AgIn)xZn2(1-x)S2, ZAIS] as low-toxicity QDs were fabricated and their electroluminescence properties were investigated. The ZAIS QDs exhibited red photoluminescence, with a peak wavelength of ca. 700 nm. Because the charge-injection barrier of ZAIS QDs without a wide-bandgap shell is relatively low, the QD-LEDs with red ZAIS QDs in combination with organic charge-transport materials induce electron injection from an organic electron-transport layer. These QD-LEDs exhibit an external quantum efficiency of 2.2%, a turn-on voltage of 2.4 V, and red emission with chromaticity coordinates (0.66, 0.33).