Tail state mediated conduction in zinc tin oxide thinfilm phototransistors under below bandgap optical excitation

AbstractWe report on the appearance of a strong persistent photoconductivity (PPC) and conductor-like behaviour in zinc tin oxide (ZTO) thinfilm phototransistors. The active ZTO channel layer was prepared by remote plasma reactive sputtering and possesses an amorphous structure. Under sub-bandgap excitation of ZTO with UV light, the photocurrent reaches as high as ~ 10−4 A (a photo-to-dark current ratio of ~ 107) and remains close to this high value after switching off the light. During this time, the ZTO TFT exhibits strong PPC with long-lasting recovery time, which leads the appearance of the conductor-like behaviour in ZTO semiconductor. In the present case, the conductivity changes over six orders of magnitude, from ~ 10−7 to 0.92/Ω/cm. After UV exposure, the ZTO compound can potentially remain in the conducting state for up to a month. The underlying physics of the observed PPC effect is investigated by studying defects (deep states and tail states) by employing a discharge current analysis (DCA) technique. Findings from the DCA study reveal direct evidence for the involvement of sub-bandgap tail states of the ZTO in the strong PPC, while deep states contribute to mild PPC.

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Tail-states induced appearance of conductor‑like behaviour in zinc‑tin‑oxide photo‑thinfilm transistors under sub-bandgap light excitation

10.21203/rs.3.rs-540352/v1 ◽

2021 ◽

Author(s):

Soumen Dhara ◽

Kham Niang ◽

Andrew Flewitt ◽

Arokia Nathan ◽

Stephen Lynch

Keyword(s):

Tin Oxide ◽

Dark Current ◽

Direct Evidence ◽

Uv Light ◽

Amorphous Structure ◽

Persistent Photoconductivity ◽

Current Analysis ◽

Current Ratio ◽

Zinc Tin Oxide ◽

Light Excitation

Abstract We report on a strong persistent photoconductivity (PPC) induced appearance of conductor‑like behaviour in zinc-tin-oxide (ZTO) photo-thinfilm transistors (TFT). The active ZTO channel layer was prepared by remote-plasma reactive sputtering and possesses an amorphous structure. Under sub-bandgap excitation of ZTO with UV light, the photocurrent reaches as high as ~10-4 A (a photo-to-dark current ratio of ~107) and remains close to this high value after switching off the light. During this time, the ZTO TFT exhibits strong PPC with long-lasting recovery time, which leads the appearance of the conductor‑like behaviour in ZTO semiconductor. In the present case, the conductivity changes over six orders of magnitude, from ~10-7 to 0.92 Ω-1cm-1. After UV exposure, the ZTO compound can potentially remain in the conducting state for up to a month. The underlying physics of the observed PPC effect is investigated by studying defects (deep-states and tail-states) by employing a discharge current analysis (DCA) technique. Findings from the DCA study reveal direct evidence for the involvement of sub-gap tail-states of the ZTO in the strong PPC, while deep-states contribute to mild PPC.

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Ultra-Flexible Organic Solar Cell Based on Indium-Zinc-Tin Oxide Transparent Electrode for Power Source of Wearable Devices

Nanomaterials ◽

10.3390/nano11102633 ◽

2021 ◽

Vol 11 (10) ◽

pp. 2633

Author(s):

Jun Young Choi ◽

In Pyo Park ◽

Soo Won Heo

Keyword(s):

Tin Oxide ◽

Incident Angle ◽

Flexible Substrate ◽

Chemical Vapor ◽

Transparent Electrode ◽

Amorphous Structure ◽

Wearable Devices ◽

Power Source ◽

Hole Transport ◽

Zinc Tin Oxide

We have developed a novel structure of ultra-flexible organic photovoltaics (UFOPVs) for application as a power source for wearable devices with excellent biocompatibility and flexibility. Parylene was applied as an ultra-flexible substrate through chemical vapor deposition. Indium-zinc-tin oxide (IZTO) thin film was used as a transparent electrode. The sputtering target composed of 70 at.% In2O3-15 at.% ZnO-15 at.% SnO2 was used. It was fabricated at room temperature, using pulsed DC magnetron sputtering, with an amorphous structure. UFOPVs, in which a 1D grating pattern was introduced into the hole-transport and photoactive layers were fabricated, showed a 13.6% improvement (maximum power conversion efficiency (PCE): 8.35%) compared to the reference device, thereby minimizing reliance on the incident angle of the light. In addition, after 1000 compression/relaxation tests with a compression strain of 33%, the PCE of the UFOPVs maintained a maximum of 93.3% of their initial value.

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Photoresponses of Zinc Tin Oxide Thin-Film Transistor

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2020.17159 ◽

2020 ◽

Vol 20 (3) ◽

pp. 1704-1708

Author(s):

Wei Lun Huang ◽

Chen-Chuan Yang ◽

Sheng-Po Chang ◽

Shoou-Jinn Chang

Keyword(s):

Thin Film ◽

Tin Oxide ◽

Thin Film Transistor ◽

Drain Current ◽

Oxide Thin Film ◽

Current Ratio ◽

Uv Photodetector ◽

Saturation Region ◽

Zinc Tin Oxide ◽

Sputtering System

In this study, the optical and electrical properties of a zinc tin oxide (ZTO) thin-film transistor (TFT) were investigated. The TFT was fabricated using ZTO as the active layer, which was deposited by a radio frequency magnetron sputtering system, to form an ultraviolet (UV) photodetector. The device has a threshold voltage of 0.48 V, field-effect mobility of 1.47 cm2/Vs in the saturation region, on/off drain current ratio of 2×106, and subthreshold swing of 0.45 V/decade in a dark environment. Moreover, as a UV photodetector, the device has a long photoresponse time, responsivity of 0.329 A/W, and rejection ratio of 3.19×104 at a gate voltage of -15 V under illumination of wavelength 300 nm.

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