Utilizing VO₂ as a Hole Injection Layer for Efficient Charge Injection in Quantum Dot Light-Emitting Diodes Enables High Device Performance

Abstract

Quantum dot light-emitting diodes (QLEDs) are promising devices for display applications. Polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) is a common hole injection layer (HIL) material in optoelectronic devices because of its high conductivity and high work function. Nevertheless, PEDOT:PSS-based QLEDs have a high energy barrier for hole injection, which results in low device efficiency. Therefore, a new strategy is needed to improve the device efficiency. Herein, we have demonstrated a bilayer-HIL using VO2 and a PEDOT:PSS-based QLED that exhibits an 18% external quantum efficiency (EQE), 78 cd/A current efficiency (CE), and 25,771 cd/m2 maximum luminance. In contrast, the PEDOT:PSS-based QLED exhibits an EQE of 13%, CE of 54 cd/A, and maximum luminance of 14,817 cd/m2. An increase in EQE was attributed to a reduction in the energy barrier between indium tin oxide (ITO) and PEDOT:PSS, caused by the insertion of a VO2 HIL. Therefore, our results could demonstrate that using a bilayer-HIL is effective in increasing the EQE in QLEDs.

Advanced HIL strategies in QLEDs: V2O5 and PEDOT:PSS dual-layer for charge balance and electron leakage prevention

“…In our previous study, the difference in refractive indices between ITO ( n = 1.5) and PEDOT:PSS ( n = 1.95) caused photons generated within the EML to undergo refraction and reflection, consequently diminishing the luminance in PEDOT:PSS-based QLED. 38 However, the refractive index of V 2 O 5 (∼1.9) allowed for some optical adjustments, enabling photons to be emitted more directly, increasing luminance. Moreover, when the refractive indices and thicknesses were considered in the luminance simulations, the luminance values calculated with V 2 O 5 were approximately 2% higher (Fig.…”