Ultrafast Charge Carrier Dynamics and Transport Characteristics in HgTe Quantum Dots

作者：Sergeeva, Kseniia A.; Fan, Kezhou; Sergeev, Aleksandr A.; Hu, Sile; Liu, Haochen; Chan, Christopher C.; Kershaw, Stephen V.; Wong, Kam Sing^*; Rogach, Andrey L.^*

来源：Journal of Physical Chemistry C, 2022, 126(45): 19229-19239.

DOI：10.1021/acs.jpcc.2c05348

• EMISSION
• PHOTOLUMINESCENCE
• NANOCRYSTALS
• EXCITON

We investigate the charge carrier dynamics in HgTe quantum dots emitting in the second near-infrared window (1000-2500 nm). To provide a link between fundamental physics and practical application, we made consistent studies of the charge carrier dynamics evolution for quantum dots in different states: colloidal solutions of quantum dots capped with a long-chain ligand; thin films made from them; and finally, exchanged to short-chain ligand films suitable for field effect transistor based devices. Ultrafast transient absorption spectroscopy reveals an ultralow Auger-related nonradiative relaxation threshold at 0.1 exciton per quantum dot, both in colloidal solutions and solid films, with a rate of 30 ns-1. The exchange from long-to short-chain ligands causing closer packing of the HgTe quantum dots leads to a strong increase of the Auger recombination rate of up to 100 ns-1. The competition between the Auger process and excitonic recombination significantly affects the performance of HgTe-based thin film photodetectors operating at room temperature, resulting in a 2 orders of magnitude drop in responsivity when the excitation flux was increased from 0.01 to 5 W center dot cm-2.