Defect studies on short-wave infrared photovoltaic devices based on HgTe nanocrystals/TiO2heterojunction

Sreeshma, D and Janani, B and Jagtap, A and Abhale, A and Rao, KSRK (2020) Defect studies on short-wave infrared photovoltaic devices based on HgTe nanocrystals/TiO2heterojunction. In: Nanotechnology, 31 (38).

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Abstract

Narrow bandgap (<0.5 eV) colloidal semiconductor nanocrystals (e.g. mercury chalcogenides) provide practical platforms for next generation short wave infrared, mid wave infrared and long wave infrared optoelectronic devices. Until now, most of the efforts in the field of infrared active nanocrystals have been taken on synthesizing nanocrystals, determining quantum states and building different geometries for optoelectronic devices. However, studies on interface trap states in the devices made from these narrow band gap nanocrystals are mostly unexplored. Herein, we investigate the defects or traps in these nanocrystals-embedded devices, which will be critical for improving their optoelectronic performance. In this article, we fabricate HgTe nanocrystals/TiO2 based photovoltaic devices and used capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) to investigate and obtain quantitative information on deep level trap states. Interestingly, frequency dependent C-V measurements show two peaks in the capacitance at lower frequency (<40 kHz), which is attributed to the presence of trap states. However, at high frequency the presence of a weak hump-like structure almost at the center of above two peaks validate the role of interface traps. DLTS studies show that traps at the interface of HgTe nanocrystals/TiO2 acts as recombination centers having activation energies of 0.27, 0.4 and 0.45 eV with corresponding trap densities of 1.4 � 1010, 1.9 � 1011 and 1.5 � 1011 cm-3 and estimated capture cross-sections of 6.3 � 10-14, 7.5 � 10-17 and 3.7 � 10-14 cm2, respectively. In this work, DLTS has revealed the existence of interface trap states and the frequency dependent capacitance measurements corroborate the effect of charge storage on the heterostructures built from these nanocrystals that helps in the development of futuristic devices. © 2020 IOP Publishing Ltd.

Item Type:	Journal Article
Publication:	Nanotechnology
Publisher:	Institute of Physics Publishing
Additional Information:	Copy right for this article belongs to Institute of Physics Publishing
Keywords:	Activation energy; Capacitance; Capacitance measurement; Deep level transient spectroscopy; Defects; Energy gap; Infrared radiation; Inorganic compounds; Mercury compounds; Nanocrystals; Narrow band gap semiconductors; Optoelectronic devices; Quantum theory; Semiconductor devices; Titanium compounds, Capture cross sections; Colloidal semiconductor nanocrystals; Frequency-dependent capacitance; Interface trap state; Mid wave infrared (MWIR); Photovoltaic devices; Quantitative information; Recombination centers, Interface states
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	23 Dec 2020 08:46
Last Modified:	23 Dec 2020 08:46
URI:	http://eprints.iisc.ac.in/id/eprint/66142

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