Band alignment and band bending at α-Ga2O3/ZnO n-n isotype hetero-interface

ABSTRACTFormation of a low barrier back contact plays a critical role in improving the photoconversion efficiency of the CdTe solar cells. Incorporating a buffer layer to minimize the band bending at the back of the CdTe device can significantly lower the barrier for the hole current, improving open circuit voltage (VOC) and the fill factor. Over the past years, researchers have incorporated the both ZnTe and Te as buffer layers to improve CdTe device performance. Here we compare device performance using these two materials as buffer layers at the back of CdTe devices. We show that using Te in contact to CdTe results in higher performance than using ZnTe in contact to the CdTe. Low temperature current density-voltage measurements show that Te results is a lower barrier with CdTe than ZnTe, indicating that Te has better band alignment, resulting in less downward bending in the CdTe at the back interface, than ZnTe does.

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Sb2S3/TiO2 Heterojunction Photocathodes: Band Alignment and Water Splitting Properties

10.26434/chemrxiv.12110208 ◽

2020 ◽

Author(s):

Rajiv Ramanujam Prabhakar ◽

Thomas Moehl ◽

Sebastian Siol ◽

Jihye Suh ◽

David Tilley

Keyword(s):

Buffer Layer ◽

Water Splitting ◽

Elemental Sulfur ◽

Band Alignment ◽

Band Bending ◽

Co Catalyst ◽

Conduction Band Offset ◽

Photovoltaic Applications ◽

Earth Abundant ◽

Further Development

Antimony sulfide (Sb2S3) is a promising light absorbing semiconductor for photovoltaic applications, though it remains vastly unexplored for photoelectrochemical water splitting. Sb2S3 was synthesized by a simple sulfurization of electrodeposited antimony metal at relatively low temperatures (240-300°C) with elemental sulfur. Using a TiO2 buffer layer and a platinum co-catalyst, photocurrent densities up to ~ 9 mA cm-2 were achieved at -0.4 V vs. RHE in 1 M H2SO4 under one sun illumination. Using XPS band alignment studies and potential dependent IPCE measurements, a conduction band offset of 0.7 eV was obtained for the Sb2S3/TiO2 junction as well as an unfavorable band bending at the heterointerface, which explains the low photovoltage that was observed (~ 0.1 V). Upon inserting an In2S3 buffer layer, which offers a better band alignment, a 0.15 V increase in photovoltage was obtained. The excellent PEC performance and the identification of the origin of the low photovoltage of the Sb2S3 photocathodes in this work pave the way for the further development of this promising earth abundant light absorbing semiconductor for solar fuels generation.

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Band Bending Mechanism in CdO/Arsenene Heterostructure: A Potential Direct Z-scheme Photocatalyst

Frontiers in Chemistry ◽

10.3389/fchem.2021.788813 ◽

2021 ◽

Vol 9 ◽

Author(s):

Kai Ren ◽

Ruxin Zheng ◽

Jin Yu ◽

Qingyun Sun ◽

Jianping Li

Keyword(s):

First Principles ◽

2D Materials ◽

Layered Materials ◽

Band Alignment ◽

Type Ii ◽

Band Bending ◽

Application Range ◽

Bending Mechanism ◽

Vdw Heterostructure ◽

Vdw Interaction

For the few years, two-dimensional (2D) materials have aroused general focus. In order to expand the properties and application range of 2D materials, two different layered materials are usually combined into heterostructure through van der Waals (vdW) interaction. In this research, based on first-principles simulation, we propose CdO/Arsenene (CdO/As) vdW heterostructure as a semiconductor possessing a direct bandgap by 2.179 eV. Besides, the CdO/As vdW heterostructure presents type-II band alignment, which can be used as a remarkable photocatalyst. Importantly, the CdO/As heterostructure demonstrates a direct Z-type principle photocatalyst by exploring the band bending mechanism in the heterostructure. Furthermore, we calculated the light absorption characteristics of CdO/As vdW heterostructure by optical absorption spectrum and conversion efficiency of a novel solar-to-hydrogen efficiency (ηSTH) about 11.67%, which is much higher than that of other 2D photocatalysts. Our work can provide a theoretical guidance for the designing of Z-scheme photocatalyst.

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Role of Surfaces and Interfaces for the Electronic Properties of Conducting Oxides

MRS Proceedings ◽

10.1557/proc-666-f1.10 ◽

2001 ◽

Vol 666 ◽

Cited By ~ 7

Author(s):

Andreas Klein

Keyword(s):

Work Function ◽

Electronic Properties ◽

Photoelectron Spectroscopy ◽

Band Alignment ◽

Surface Band ◽

Band Bending ◽

Conducting Oxides ◽

Degenerate Semiconductors ◽

Surfaces And Interfaces

ABSTRACTTransparent conductive oxides (TCOs) are generally considered as degenerate semiconductors doped intrinsically by oxygen vacancies and by intentionally added dopants. For some applications a high work function is required in addition to high conductivity and it is desired to tune both properties independently. To increase the work function, the distance between the Fermi energy and the vacuum level must increase, which can be realized either by electronic surface dipoles or by space charge layers. Photoelectron spectroscopy data of in-situ prepared samples clearly show that highly doped TCOs can show surface band bending of the order of 1 eV. It is further shown that the band alignment at heterointerfaces between TCOs and other materials, which are crucial for many devices, are also affected by such band bending. The origin of the band bending, which seems to be general to all TCOs, depends on TCO thin film and surface processing conditions. The implication of surface band bending on the electronic properties of thin films and interfaces are discussed.

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Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Journal of Applied Physics ◽

10.1063/1.4895985 ◽

2014 ◽

Vol 116 (12) ◽

pp. 123702 ◽

Cited By ~ 44

Author(s):

Jialing Yang ◽

Brianna S. Eller ◽

Robert J. Nemanich

Keyword(s):

Gallium Nitride ◽

Atomic Layer ◽

Band Alignment ◽

Surface Band ◽

Band Bending

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Band alignment investigations of heterostructure NiO/TiO2 nanomaterials used as efficient heterojunction earth-abundant metal oxide photocatalysts for hydrogen production

Physical Chemistry Chemical Physics ◽

10.1039/c7cp01300k ◽

2017 ◽

Vol 19 (29) ◽

pp. 19279-19288 ◽

Cited By ~ 52

Author(s):

Md. T. Uddin ◽

Y. Nicolas ◽

C. Olivier ◽

W. Jaegermann ◽

N. Rockstroh ◽

...

Keyword(s):

Hydrogen Production ◽

Metal Oxide ◽

Band Alignment ◽

Band Bending ◽

Earth Abundant ◽

Tio2 Nanomaterials

Earth-abundant NiO/TiO2 heterostructures lead to enhanced H2 production by methanol photoreforming due to favorable band bending at the interface of the NiO/anatase TiO2 p–n heterojunction.

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Energy band alignment at the heterointerface between CdS and Ag-alloyed CZTS

Scientific Reports ◽

10.1038/s41598-020-73828-0 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Mungunshagai Gansukh ◽

Zheshen Li ◽

Moises Espindola Rodriguez ◽

Sara Engberg ◽

Filipe Mesquita Alves Martinho ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Energy Band ◽

Depth Profiling ◽

Band Alignment ◽

Nanometer Scale ◽

Significant Shift ◽

Total Charge ◽

Band Bending ◽

Conduction Band Offset ◽

Depletion Width

Abstract Energy band alignment at the heterointerface between CdS and kesterite Cu2ZnSnS4 (CZTS) and its alloys plays a crucial role in determining the efficiency of the solar cells. Whereas Ag alloying of CZTS has been shown to reduce anti-site defects in the bulk and thus rise the efficiency, the electronic properties at the interface with the CdS buffer layer have not been extensively investigated. In this work, we present a detailed study on the band alignment between n-CdS and p-CZTS upon Ag alloying by depth-profiling ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). Our findings indicate that core-level peaks and the valence band edge of CdS exhibit a significant shift to a lower energy (larger than 0.4 eV) upon the etching of the CdS layer, which can be assigned due to band bending and chemical shift induced by a change in the chemical composition across the interface. Using a simplified model based on charge depletion layer conservation, a significantly larger total charge region depletion width was determined in Ag-alloyed CZTS as compared to its undoped counterpart. Our findings reveal a cliff-like band alignment at both CdS/CZTS and CdS/Ag-CZTS heterointerfaces. However, the conduction-band offset decreases by more than 0.1 eV upon Ag alloying of CZTS. The approach demonstrated here enables nanometer-scale depth profiling of the electronic structure of the p–n junction and can be universally applied to study entirely new platforms of oxide/chalcogenide heterostructures for next-generation optoelectronic devices.

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Measurements of the Band Offset of SiO2 on Clean GaN

MRS Proceedings ◽

10.1557/proc-693-i9.10.1 ◽

2001 ◽

Vol 693 ◽

Author(s):

E.H. Hurt ◽

Ted E. Cook ◽

K.M. Tracy ◽

R.F. Davis ◽

G. Lucovsky ◽

...

Keyword(s):

Molecular Beam ◽

Electronic States ◽

Band Alignment ◽

Gate Insulator ◽

Band Offset ◽

Valence Band Offset ◽

Band Bending ◽

Analysis Techniques ◽

Conduction Band Offset ◽

Surface Analysis Techniques

AbstractThe band alignment of SiO2 and GaN is important for passivation of high voltage devices and for gate insulator applications. In this study XPS and UPS techniques are employed to determine the electronic states as SiO2 is deposited onto a clean GaN surface. The substrate was epitaxially grown n-type GaN on 6H-SiC (0001) substrates with an AlN (0001) buffer layer. The GaN surface was atomically cleaned via a 860°C anneal in an NH3 atmosphere. For the clean GaN surface, upward band bending of ~0.3 ±0.1 eV was measured, and the electron affinity was measured to be ~2.9 eV. Layers of Si were deposited on the GaN surface via Molecular Beam Epitaxy (MBE), and the Si was oxidized by a remote O2 plasma. The oxidation of the Si occurred without oxidizing the GaN. Densification of the created SiO2 film was achieved by annealing the substrate at 650°C. Surface analysis techniques were performed after each process, and yielded a valence band offset of ~2.0 eV, and a conduction band offset of ~3.6 eV for the GaN-SiO2 interface.

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Band bending and band alignment at HfO 2 /HfSi x O y /Si interfaces

Applied Surface Science ◽

10.1016/j.apsusc.2006.07.054 ◽

2007 ◽

Vol 253 (7) ◽

pp. 3508-3511 ◽

Cited By ~ 6

Author(s):

Weijie Song ◽

Michiko Yoshitake ◽

Ruiqin Tan ◽

Isao Kojima

Keyword(s):

Band Alignment ◽

Band Bending

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