Investigations of defect levels in different sized HgTe nanocrystals based photovoltaic devices using thermal admittance spectroscopy

Sreeshma, D and Jagtap, A and Balakrishnan, J and Chandra Mallik, R and Koteswara Rao, KSR (2023) Investigations of defect levels in different sized HgTe nanocrystals based photovoltaic devices using thermal admittance spectroscopy. In: Journal of Applied Physics, 133 (24).

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Abstract

HgTe nanocrystals (NCs) have unique properties that make them suitable for optoelectronic devices in the mid-wave infrared (MWIR) and short-wave infrared regions. However, electrically active defects can trap charge carriers, reducing their mobility and diffusion length, which degrades the NCs’ optical and electrical properties. In this study, we used the thermal admittance spectroscopic (TAS) method to analyze defects in HgTe NC-based photovoltaic devices. The ITO/HgTe/Al device structure was used to study the defect levels in HgTe nanocrystals and the effect of these traps on transport properties. Using low-temperature I-V measurements, we calculated the trap activation energy as 0.14 eV, and the transport was found to occur mainly through these trap states. From the TAS measurements, the trap activation energy obtained was 0.14 eV, and the concentration of trap level was 3.16 × 10 16 cm − 3 eV − 1 . We have also fabricated ITO/ TiO 2 /HgTe/Au and fluorine doped tin oxide/ TiO 2 /HgTe/ MoO 3 /Au devices and did TAS measurements to understand the effect of adding electron and hole extraction layer on the formation of defect levels. Intriguingly, a distinct reversal in the capacitance-frequency (C-F) behavior is observed at different temperatures, leading to positive slopes in the Arrhenius plot. This peculiar phenomenon is attributed to the size-dependent doping effects within the HgTe nanocrystals. The outcomes of this study shed light on the significance of understanding and quantifying electrically active defects in HgTe nanocrystals for the advancement of NC-based optoelectronic devices.

Item Type:	Journal Article
Publication:	Journal of Applied Physics
Publisher:	American Institute of Physics Inc.
Additional Information:	The copyright for this article belongs to the American Institute of Physics Inc.
Keywords:	Arrhenius plots; Carrier mobility; Defects; Infrared radiation; Mercury compounds; Nanocomposites; Nanocrystals; Temperature; Tin oxides, Defect levels; Electrically active defects; Optoelectronics devices; Photovoltaic devices; Property; Short wave infrared regions; Spectroscopic measurements; Thermal admittance; Thermal admittance spectroscopy; TiO 2, Activation energy
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	28 Jul 2023 08:48
Last Modified:	28 Jul 2023 08:48
URI:	https://eprints.iisc.ac.in/id/eprint/82577

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