Improving the performance of quantum-dot light-emitting diodes via an organic–inorganic hybrid hole injection layer

Poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) is a commonly used material for the hole injection layer (HIL) in quantum-dot light-emitting diodes (QLEDs). In this work, we improved the performance of the QLED by using an organic–inorganic hybrid HIL. The hybrid HIL was prepared by mixing PEDOT:PSS with vanadium oxide (V(2)O(5)), which is a transition-metal oxide (TMO). The hole injection properties of PEDOT:PSS were improved according to the amount of V(2)O(5) mixed into the PEDOT:PSS. The maximum luminance and current efficiency were 36 198 cd m(−2) and 13.9 cd A(−1), respectively, when the ratio of PEDOT:PSS and V(2)O(5) was 10 : 1. Moreover, the operating lifetime exceeded 300 h, which is 10 times longer than the lifetime of the device with only PEDOT:PSS HIL. The improvement was analyzed using ultraviolet and X-ray photoelectron spectroscopy. We found that the density of state (DOS) of PEDOT:PSS near the Fermi energy level was increased by mixing V(2)O(5). Therefore, the increase of DOS improved the hole injection and the performance of QLEDs. The result shows that the hybrid HIL can improve the performance and the stability of QLEDs.