Computational Carrier Dynamics across Heterojunction Interface between Hole Injection and Transport Layers in Quantum-Dot Light-Emitting Diodes

Abstract

Physics-based charge transport modelling is widely used to analyse multilayer optoelectronic devices. However, conventional drift–diffusion discretisation schemes can exhibit numerical instability at heterojunction interfaces with abrupt discontinuities in energy levels and doping density. In quantum-dot light-emitting diodes (QD-LEDs), the heterojunction between the hole injection layer (HIL) and the hole transport layer (HTL) represents such a critical interface. In this study, a field-dependent current density scheme is proposed to stabilise the discretisation of drift-diffusion currents across heterojunction interfaces. By incorporating the local electric-field direction when evaluating carrier densities at discretised boundaries, the scheme suppresses numerical artefacts associated with mean-value interpolation of the carrier density. The stability and convergence of our model are examined using a one-dimensional finite-difference framework and subsequently implemented in a charge transport model for QD-LEDs. Using this model, the effects of energy-level alignment and acceptor doping density at the HIL/HTL interface on charge transport and electro-optical characteristics are analysed. The simulations reproduce typical voltage-dependent experimental trends in current density, luminance, and external quantum efficiency, providing insight into the role of the HIL/HTL heterojunction in carrier injection. Owing to its numerical formulation, the proposed approach is applicable to a broad range of multilayer semiconductor devices involving heterojunction interfaces.