Unraveling the hole injection mechanism of organic/quantum-dot heterointerfaces
Qi Shen, Xiaojuan Sun, Xingtong Chen, Rui Li, Xinrui Li, Song Chen
Abstract
For colloidal quantum dot (CQD) electronics, the physics of hole injection across organic/CQD heterointerfaces (OQHs) plays a fundamental role in determining device performance. Classical semiconductor theories have failed to predict device characteristics accurately, and it is essential to develop a model that prioritizes the OQH’s localized and distributed electronic states. Using an iterative electrostatic model and ultraviolet photoelectron spectroscopy, we find that the interface energy-level offset is less than previously thought due to disorder-driven charge transfer. Combining density-of-states (DOS) distributions with hopping dynamics, we find that holes predominantly hop from the organics’ DOS maximum to the CQDs’ tail states, which challenges the conventional assumption of charges hopping from the Fermi level. The electrostatic and dynamic effects combine a barrier reduction of over 0.35 eV. Our model’s predicted current-field characteristics match well with those measured from hole-only devices and help to provide a universal explanation for hole injection in CQD-based electronic devices.