Effect of Plasma Treatment on Metal Oxide p–n Thin Film Diodes Fabricated at Room Temperature

Abstract

There is a need for a good quality thin film diode using a metal oxide p–n heterojunction as it is an essential component for the realization of flexible large‐area electronics. However, metal oxide‐based diodes normally show poor rectification characteristics whose origin is still poorly understood; this is holding back their use in various applications. A systematic study of the origins of the poor performance is performed based on bias‐stress measurements using a cuprous oxide (Cu2O)/amorphous zinc‐tin oxide (a‐ZTO) heterojunction as an example. This suggests that multiple carrier trapping and thermal release of carriers in defect states stemming from oxygen vacancies at the heterojunction interface is the primary cause of poor rectification. It is demonstrated that a plasma treatment is an effective way to optimize the population of oxygen vacancies at the heterojunction interface based on extensive material analyses, allowing a significant improvement in the diode performance with a much‐enhanced rectification ratio from ≈20 to 10 000, and a consequent facilitation of the next‐generation of ubiquitous electronics.

Doping Density Extraction of Plasma Treated Metal Oxide Thin Film Diodes by Capacitance–Voltage Analysis

“…Reproduced under terms of the CC‐BY license. [ 17 ] 2021, Y. J. Khong, K. M. Niang, S. Han, N. J. Coburn, G. Wyatt‐Moon, A. J. Flewitt, published by Wiley.…”

“…This observed outcomes may be explained by the shift in equilibrium in the conversion process between ionised oxygen vacancies and electron‐filled states. [ 17 ] The majority of charge carrier contributors in the a‐ZTO layer of the untreated diode are states in the metal oxide constantly shifting between oxygen vacancy states and electron‐filled states depending on Fermi level position favouring the generation of either one. When the alternating current signal from C–V measurement increases, these states are no longer able to follow, and the apparent doping density increases.…”

“…[25,26] The precise fabrication and plasma treatment procedures of the diodes, along with the process and equipment involved were detailed in the previously published work. [17] Many samples were previously fabricated, tested, and optimized prior to the devices involved in this publication. However, in this study only one device per category was fabricated and characterized.…”

The NiO/CuInS2 Quantum Dots/ZnO Orderly Nanoarrays Transparent Pn Junction Towards Enhanced Photovoltaic Conversion via Dual Functional CuInS2 QDs

“…Especially the green and sufficient solar energy would be the most ideal candidate, [5][6][7][8] such as photocatalytic hydrogen evolution, photocatalytic CO 2 reduction to CH 4 or CO, or solar water heater, and so on. Herein, the photovoltaic device with directly photoelectric conversion would be an efficient method, [9][10][11] such as Emetere et al have reported NaZnBr 3 -based novel perovskite solar cells, [12] etc. However, the traditional photovoltaic devices mainly aim at the ultimate photovoltaic conversion efficiency, that, the adequately solar absorption would lead a significant decreasing in lighting, which would restrict their widely applications, especially in windows or building walls.…”

“…Especially the green and sufficient solar energy would be the most ideal candidate, [ 5–8 ] such as photocatalytic hydrogen evolution, photocatalytic CO 2 reduction to CH 4 or CO, or solar water heater, and so on. Herein, the photovoltaic device with directly photoelectric conversion would be an efficient method, [ 9–11 ] such as Emetere et al. have reported NaZnBr 3 ‐based novel perovskite solar cells, [ 12 ] etc.…”