Computational carrier dynamics across heterojunction interface between hole injection and transport layers in quantum-dot light-emitting diodes

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.