Band alignment at CdS/wide-band-gap Cu(In,Ga)Se2 hetero-junction by using PES/IPES

2005 ◽  
Vol 865 ◽  
Author(s):  
S.H. Kong ◽  
H. kashiwabara ◽  
K. Ohki ◽  
K. Itoh ◽  
T. Okuda ◽  
...  
Keyword(s):  
Band Gap ◽  
Conduction Band ◽  
Ion Beam ◽  
Wide Band ◽  
Valence Band Maximum ◽  
Conduction Band Minimum ◽  
Band Alignment ◽  
Interface Region ◽  
Photoemission Spectroscopy ◽  
Wide Gap

AbstractDirect characterization of band alignment at chemical bath deposition (CBD)-CdS/Cu0.93 (In1-xGax)Se2 has been carried out by photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). Ar ion beam etching at the condition of the low ion kinetic energy of 350 eV yields a removal of surface contamination as well as successful measurement of the intrinsic properties of each layer and the interfaces. Especially interior regions of the wide gap CIGS layers with a band gap of 1.4 ∼ 1.6 eV were successfully exposed. IPES spectra revealed that the conduction band offset (CBO) at the interface region of the wide gap CIGS with x = 0.60 and 0.75 was negative, where the conduction band minimum of CdS was lower than that of CIGS. It was also observed that the energy spacing between conduction band minimum (CBM) of CdS layer and valence band maximum (VBM) of Cu0.93(In0.25Ga0.75)Se2 layer at interface region was no wider than that of the interface over the Cu0.93(In0.60Ga0.40)Se2 layer.

Study of Band Alignment at CBD-CdS/Cu(In1-xGax)Se2 (x = 0.2 - 1.0) Interfaces by Photoemission and Inverse Photoemission Spectroscopy

2007 ◽  
Vol 1012 ◽  
Author(s):  
Shimpei Teshima ◽  
Hirotake Kashiwabara ◽  
Keimei Masamoto ◽  
Kazuya Kikunaga ◽  
Kazunori Takeshita ◽  
...  
Keyword(s):  
Band Gap ◽  
Conduction Band ◽  
Valence Band Maximum ◽  
Band Gap Energy ◽  
Band Alignment ◽  
Photoemission Spectroscopy ◽  
Gap Energy ◽  
Conduction Band Offset ◽  
Inverse Photoemission ◽  
Inverse Photoemission Spectroscopy

AbstractDependence of band alignments at interfaces between CdS by chemical bath deposition and Cu(In1-xGax)Se2 by conventional 3-stage co-evaporation on Ga substitution ratio x from 0.2 to 1.0 has been systematically studied by means of photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). For the specimens of the In-rich CIGS, conduction band minimum (CBM) by CIGS was lower than that of CdS. Conduction band offset of them was positive about +0.3 ~ +0.4 eV. Almost flat conduction band alignment was realized at x = 0.4 ~ 0.5. On the other hand, at the interfaces over the Ga-rich CIGS, CBM of CIGS was higher than that of CdS, and CBO became negative. The present study reveals that the decrease of CBO with a rise of x presents over the wide rage of x, which results in the sign change of CBO around 0.4 ~ 0.45. In the Ga-rich interfaces, the minimum of band gap energy, which corresponded to energy spacing between CBM of CdS and valence band maximum of CIGS, was almost identical against the change of band gap energy of CIGS. Additionally, local accumulation of oxygen related impurities was observed at the Ga-rich samples, which might cause the local rise of band edges in central region of the interface.

Remarkable Cd-free Sb2Se3 solar cell yield by interface band-alignment and growth orientation screening

2021 ◽  
Author(s):  
Weihuang Wang ◽  
Zixiu Cao ◽  
Huanhuan Wang ◽  
Jingshan Luo ◽  
Yi Zhang
Keyword(s):  
Solar Cell ◽  
Band Gap ◽  
Wide Band ◽  
Band Alignment ◽  
Cell Yield ◽  
Wide Band Gap ◽  
Growth Orientation ◽  
Photoelectrical Properties ◽  
Photovoltaic Material

Sb2Se3, as an alternative potential photovoltaic material, has attracted a lot of attention in recent years owing to its excellent photoelectrical properties. The eco-friendly TiO2 with wide band gap is...

scholarly journals Electronic properties of the Sn1−xPbxO alloy and band alignment of the SnO/PbO system: a DFT study

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
N. Kelaidis ◽  
S. Bousiadi ◽  
M. Zervos ◽  
A. Chroneos ◽  
N. N. Lathiotakis
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Density Functional ◽  
Hydrogen Generation ◽  
Valence Band Maximum ◽  
Oxide System ◽  
Band Alignment ◽  
Oxide Thin Film ◽  
Ternary Oxide ◽  
P Type

Abstract Tin monoxide (SnO) has attracted attention due to its p-type character and capability of ambipolar conductivity when properly doped, properties that are beneficial for the realization of complementary oxide thin film transistors technology, transparent flexible circuits and optoelectronic applications in general. However, its small fundamental band gap (0.7 eV) limits its applications as a solar energy material, therefore tuning its electronic properties is necessary for optimal performance. In this work, we use density functional theory (DFT) calculations to examine the electronic properties of the Sn1−xPbxO ternary oxide system. Alloying with Pb by element substitution increases the band gap of SnO without inducing defect states in the band gap retaining the anti-bonding character of the valence band maximum which is beneficial for p-type conductivity. We also examine the properties of the SnO/PbO heterojunction system in terms of band alignment and the effect of the most common intrinsic defects. A broken gap band alignment for the SnO/PbO heterojunction is calculated, which can be attractive for energy conversion in solar cells, photocatalysis and hydrogen generation.

scholarly journals Electron Band Alignment at Interfaces of Semiconductors with Insulating Oxides: An Internal Photoemission Study

2014 ◽  
Vol 2014 ◽  
pp. 1-30 ◽  
Author(s):  
Valeri V. Afanas'ev
Keyword(s):  
Valence Band ◽  
High Mobility ◽  
Band Alignment ◽  
Photoemission Spectroscopy ◽  
Light Elements ◽  
Bandgap Width ◽  
Electron Band ◽  
Internal Photoemission ◽  
Wide Gap ◽  
Photoemission Study

Evolution of the electron energy band alignment at interfaces between different semiconductors and wide-gap oxide insulators is examined using the internal photoemission spectroscopy, which is based on observations of optically-induced electron (or hole) transitions across the semiconductor/insulator barrier. Interfaces of various semiconductors ranging from the conventional silicon to the high-mobility Ge-based (Ge,Si1-xGex,Ge1-xSnx) andAIIIBVgroup (GaAs,InxGa1-xAs, InAs, GaP, InP, GaSb, InSb) materials were studied revealing several general trends in the evolution of band offsets. It is found that in the oxides of metals with cation radii larger than≈0.7 Å, the oxide valence band top remains nearly at the same energy (±0.2 eV) irrespective of the cation sort. Using this result, it becomes possible to predict the interface band alignment between oxides and semiconductors as well as between dissimilar insulating oxides on the basis of the oxide bandgap width which are also affected by crystallization. By contrast, oxides of light elements, for example, Be, Mg, Al, Si, and Sc exhibit significant shifts of the valence band top. General trends in band lineup variations caused by a change in the composition of semiconductor photoemission material are also revealed.

First-Principles Calculations on the Electronic Structure of ZnO Nanowires

2012 ◽  
Vol 198-199 ◽  
pp. 23-27
Author(s):  
Nan Zhang ◽  
Hong Sheng Zhao ◽  
Dong Yang ◽  
Wen Jie Yan
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Density Functional ◽  
Valence Band Maximum ◽  
Zno Nanowires ◽  
Cross Sectional ◽  
Quantum Size

Based upon the density functional theory (DFT) in this paper, the first-principles approach is used to study the electronic structure of different cross-sectional diameters of ZnO [0001] nanowires of wurtzite structure. The results show that ZnO [0001] nanowires have a wide direct band gap. Located in the G-point of the Brillouin zone the conduction band minimum and valence band maximum are relatively smooth. The conduction band is mainly composed of Zn 4s and Zn 4p states, and the valence band is composed of Zn 3d and O 2p states. The effective mass of conduction band electrons and valence band holes are large while their mobility is very low which show that conductive ability of pure defect-free [0001] ZnO nanowires is weak. Along with the increase of the cross-sectional diameters, the band gap gradually decreases that indicates quantum size effects are obvious in the nano size range.

Study of Band Alignment at the Interface between CBD-CdS and CIGS grown by H2O-introduced co-evaporation

2007 ◽  
Vol 1012 ◽  
Author(s):  
Norio Terada ◽  
Hirotake Kashiwabara ◽  
Kazuya Kikunaga ◽  
Shimpei Teshima ◽  
Tetsuji Okuda ◽  
...  
Keyword(s):  
Conduction Band ◽  
Valence Band Maximum ◽  
Band Gap Energy ◽  
Band Alignment ◽  
Type I ◽  
Conduction Band Offset ◽  
Substitution Ratio ◽  
Band Alignments ◽  
Inverse Photoemission Spectroscopy ◽  
Ga Substitution

AbstractFor understanding the origin of the improvements of properties in the CIGS-based cells, of which the CIGS absorber has been fabricated by H2O-introduced co-evaporation [CIGS-H2O], band alignment at the interfaces between chemical bath deposited CdS and CIGS-H2O with Ga substitution ratio ~ 40 % has been studied by photoemission and inverse photoemission spectroscopy. The CdS layer over the CIGS-H2O showed an identical electronic structure with that of CdS on the conventionally grown CIGS; band gap energy of 2.3 ~ 2.4 and a location of conduction band minimum (CBM) and valence band maximum (VBM) relative to Fermi level were + 0.75 eV and -1.6 ~ -1.7 eV, respectively. In the interface region, decreases of CBM and a rise of VBM were observed. Total amount of the decrease of CBM over the interface was 0.2 ~ 0.3 eV. XPS measurements of the core-level signals over the interface showed a small upward bend bending of 0.1 ~ 0.2 eV. Consequently, the conduction band offset (CBO) and valence bad offset (VBO) at the CBD-interface over the CIGS-H2O (Ga~40%) are about +0.1, and 0.9 ~ 1.1 eV, respectively. This positive CBO is contrast with a slightly negative CBO at the interface between CBD-CdS/conventionally grown CIGS with Ga ~ 40 % measured previously. These results indicate that the H2O introduction is effective to extend the upper limit of the Ga substitution ratio where the Type-I conduction band alignment is maintained. The observed band alignments are consistent with the rise of Voc and efficiency in the CIGS-H2O based cells.

Surface and dynamical properties of GeI2

2D Materials ◽  
2021 ◽  
Author(s):  
Archit Dhingra ◽  
Alexey Lipatov ◽  
Haidong Lu ◽  
Katerina Chagoya ◽  
Joseph Dalton ◽  
...  
Keyword(s):  
Band Gap ◽  
Debye Temperature ◽  
Wide Band ◽  
Core Level ◽  
Photoemission Spectroscopy ◽  
Bulk Temperature ◽  
Level Shift ◽  
Temperature Dependent ◽  
X Ray ◽  
Optical Absorbance

Abstract GeI2 is an interesting two-dimensional (2D) wide-band gap semiconductor because of diminished edge scattering due to an absence of dangling bonds. Angle-resolved x-ray photoemission spectroscopy (ARXPS) indicates a germanium rich surface, and a surface to bulk core-level shift of 1.8 eV in binding energy, between the surface and bulk components of the Ge 2p3/2 core-level, making clear that the surface is different from the bulk. Temperature dependent studies indicate an effective Debye temperature (θD ) of 186 ± 18 K for the germanium x-ray photoemission spectroscopy (XPS) feature associated with the surface. These measurements also suggest an unusually high effective Debye temperature for iodine (587 ± 31 K), implying that iodine is present in the bulk of the material, and not the surface. From optical absorbance, GeI2 is seen to have an indirect (direct) optical band gap of 2.60 (2.8) ± 0.02 (0.1) eV, consistent with the expectations. Temperature dependent magnetometry indicates that GeI2 is moment paramagnetic at low temperatures (close to 4 K) and shows a diminishing saturation moment at high temperatures (close to 300 K and above).

Band Alignment of CdS/Cu2ZnSnSe4 Heterointerface and Solar Cell Performances

MRS Advances ◽  
2017 ◽  
Vol 2 (53) ◽  
pp. 3157-3162 ◽  
Author(s):  
Takehiko Nagai ◽  
Shinho Kim ◽  
Hitoshi Tampo ◽  
Kang Min Kim ◽  
Hajime Shibata ◽  
...  
Keyword(s):  
Conduction Band ◽  
Band Alignment ◽  
Photoemission Spectroscopy ◽  
Band Offset ◽  
Valence Band Offset ◽  
X Ray ◽  
Heterojunction Solar Cells ◽  
Conduction Band Offset ◽  
Ultraviolet Photoemission Spectroscopy ◽  
Large Spike

ABSTRACTWe determined that the conduction band offset (CBO) and the valence band offset (VBO) at the CdS/ Cu2ZnSnSe4 (CZTSe) heterointerface are +0.56 and +0.89eV, respectively, by using X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and inversed photoemission spectroscopy (IPES). A positive CBO value, so-called “spike” structure, means that the position of conduction band becomes higher than that of absorber layer. The evaluated CBO of +0.56 eV suggests that the conduction band alignment at CdS/CZTSe interface is enough to become an electron barrier. Despite such a large spike structure in the conduction band at the interface, a conversion efficiency of 8.7 % could be obtained for the CdS/CZTSe heterojunction solar cells.

In-situ Characterization of As-grown Surface of CIGS Films

2007 ◽  
Vol 1012 ◽  
Author(s):  
Hirotake Kashiwabara ◽  
Shimpei Teshima ◽  
Kazuya Kikunaga ◽  
Kazunori Takeshita ◽  
Tetsuji Okuda ◽  
...  
Keyword(s):  
Band Gap ◽  
High Performance ◽  
Identical Condition ◽  
Cell Structure ◽  
Wide Band ◽  
Surface Region ◽  
Valence Band Maximum ◽  
Wide Band Gap

AbstractIn-situ characterization of composition, electronic structure and their depth profiles of surface of Cu(In1-xGax)Se2 (CIGS) film grown by three stage co-evaporation has been carried out by means of photoemission and inverse photoemission spectroscopy (PES/IPES), for the purpose of investigating the formation mechanism of the CIGS-side wide band-gap region adjacent to CBD-CdS/CIGS interface in cell structure. Sample-transportation in vacuum below 1 x 10-8 Torr yielded almost contamination-free feature of the CIGS surface. The as-transferred surface of Cu0.93(In0.65Ga0.35)Se2 grown at the identical condition for the high performance solar cell exhibited seriously Cu and Ga deficient composition. Chemical formula of this region was inbetween Cu : (In+Ga): Se = 1 : 3 : 5 and 1 : 5 : 8. In-situ UPS/IPES measurements CIGS showed that the as-grown surface region of the CIGS already had expanded band gap energy up to 1.4 eV and n-type character. A gradual decrease of band energy and a rise of valence band maximum as a function of depth from the original surface were observed. These results have revealed that the surface of CIGS by the three stage method already has the wide band gap, which might originate in so-called Cu-vacancy ordered phase.

Highly Conductive and Wide Band GaP Microcrystalline Silicon Films Prepared by Photochemical Vapor Deposition and Applications to Devices

1985 ◽  
Vol 49 ◽  
Author(s):  
S. Nishida ◽  
H. Tasaki ◽  
M. Konagai ◽  
K. Takahashi
Keyword(s):  
Band Gap ◽  
Optical Band Gap ◽  
Wide Band ◽  
Dark Conductivity ◽  
Hydrogen Gas ◽  
Microcrystalline Silicon ◽  
Wide Band Gap ◽  
Wide Gap ◽  
P Type ◽  
Photochemical Vapor Deposition

AbstractDoped hydrogenated microcrystalline silicon (μc-Si:H) and fluorinated hydrogenated microcrystalline (μc-Si:F:H) films were prepared by the mercury photosensitized decomposition of a disilane-hydrogen or a difluorosilane-hydrogen gas mixture, respectively. The maximum dark conductivity and optical band gap of μc-Si:H films were respectively 20 S•cm−1 and ∼2.0 eV for n-type and 1 S•cm−1 and 2.3 eV for p-type. A higher dark conductivity as much as 50 S•cm−1 and a wide gap of 2.0 eV were obtained for n-type μc-Si:F:H. It is most significant that the gaseous ratio of hydrogen to disilane should be enhanced to obtain such a highly conductive and wide gap film. The crystallinity of the photo-deposited μc-Si:H films appeared to be improved in comparison with that of films by the conventional plasma glow discharge technique.

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