Investigation of quantum dots light emitting diodes with different transition metal oxide as charge injection layers

In this paper, various transition metal oxides serve as charge injection layers being prepared by solution process for the fabrication of quantum dot light emitting diodes (QLEDs) is demonstrated. Magnesium doped zinc oxide (MgZnO) nanoparticles is used as electron injection and transport layer, copper oxide (CuOx), nickel oxide (NiOx), cobalt oxide (CoOx) and molybdenum oxide (MoOx) are used as hole injection layer (HIL) for the comparison with Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS. The fabricated red QLEDs with PEDOT:PSS possess highest maximum luminance of 88,713 cd/m2 and current efficiency of 4.96 cd/A, whereas QLEDs with MoOx and NiOx HILs demonstrate lower turn on voltage of 1.5V and 2.1V and maintain decent maximum luminance of 59,699 and 64,244 cd/m2, respectively. The sub-bandgap turn-on voltage of QLED with MoOx can be attributed to thermal-assisted energy up-conversion effect due to its lower series resistance.