Carrier Transport in HgTe Colloidal Quantum Dot Solids
摘要
Charge transport in colloidal quantum dot (CQD) films is shaped by several competing factors: quantum confinement inside each dot, variations in dot electronic state energies and spacings, and applied field-induced carrier hopping from one dot site to another. Unlike extended crystalline semiconductors, these materials are made up of confined states separated by tunnel barriers, so the motion of charge is thermally activated and incoherent over experimentally relevant length scales. In this work, we examine transport using four transport models that are commonly used for disordered or confined systems: Mott variable-range hopping, Efros–Shklovskii hopping with a Coulomb gap, simple Arrhenius activation, and a more general stretched-exponential form used here as a phenomenological description of the temperature dependence. Each model highlights a different part of the transport process and is tested against temperature- and field-dependent measurements from ligand-exchanged HgTe CQD films. The data span 120–260 K and electric fields up to about 10 kV/cm. From the fits, we extract effective transport parameters including activation energy scales, mobility prefactors, effective carrier population terms, model-dependent hopping distances, and exponents that describe the temperature dependence. These fitted quantities are interpreted here as effective descriptors over the measured range rather than as uniquely assigned microscopic observables. Some models apply only within narrow physical boundaries, while others return parameters that remain stable over the measured range and are less prone to unphysical values within this dataset. This approach provides a practical framework for comparing the observed electrical behavior across different HgTe CQD morphologies and for guiding the engineering of CQD devices with improved transport characteristics.