scholarly journals Ultrafast Charge Separation in Bilayer WS2/Graphene Heterostructure Revealed by Time- and Angle-Resolved Photoemission Spectroscopy

2021 ◽  
Vol 9 ◽  
Author(s):  
Razvan Krause ◽  
Mariana Chávez-Cervantes ◽  
Sven Aeschlimann ◽  
Stiven Forti ◽  
Filippo Fabbri ◽  
...  
Keyword(s):  
Charge Separation ◽  
Graphene Layer ◽  
Optoelectronic Devices ◽  
Visible Spectral Range ◽  
Band Alignment ◽  
Photoemission Spectroscopy ◽  
Type I ◽  
Type Ii ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Indirect Band Gap

Efficient light harvesting devices need to combine strong absorption in the visible spectral range with efficient ultrafast charge separation. These features commonly occur in novel ultimately thin van der Waals heterostructures with type II band alignment. Recently, ultrafast charge separation was also observed in monolayer WS2/graphene heterostructures with type I band alignment. Here we use time- and angle-resolved photoemission spectroscopy to show that ultrafast charge separation also occurs at the interface between bilayer WS2 and graphene indicating that the indirect band gap of bilayer WS2 does not affect the charge transfer to the graphene layer. The microscopic insights gained in the present study will turn out to be useful for the design of novel optoelectronic devices.

scholarly journals Efficient Photocatalytic Hydrogen Evolution via Band Alignment Tailoring: Controllable Transition from Type-I to Type-II

Small ◽  
2017 ◽  
Vol 13 (41) ◽  
pp. 1702163 ◽  
Author(s):  
Zhongzhou Cheng ◽  
Fengmei Wang ◽  
Tofik Ahmed Shifa ◽  
Chao Jiang ◽  
Quanlin Liu ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Photocatalytic Hydrogen Evolution

Type II Band Alignment inSi1−xGex/Si(001)Quantum Wells: The Ubiquitous Type I Luminescence Results from Band Bending

1997 ◽  
Vol 79 (2) ◽  
pp. 269-272 ◽  
Author(s):  
M. L. W. Thewalt ◽  
D. A. Harrison ◽  
C. F. Reinhart ◽  
J. A. Wolk ◽  
H. Lafontaine
Keyword(s):  
Quantum Wells ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Band Bending

scholarly journals PN/PAs-WSe2 van der Waals heterostructures for solar cell and photodetector

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xinyi Zheng ◽  
Yadong Wei ◽  
Kaijuan Pang ◽  
Ngeywo Kaner Tolbert ◽  
Dalin Kong ◽  
...  
Keyword(s):  
Refractive Index ◽  
Solar Cells ◽  
Negative Refractive Index ◽  
Wide Spectrum ◽  
Van Der Waals ◽  
Band Alignment ◽  
Ultraviolet Region ◽  
Type I ◽  
Type Ii ◽  
Van Der Waals Heterostructures

Abstract By first-principles calculations, we investigate the geometric stability, electronic and optical properties of the type-II PN-WSe2 and type-I PAs-WSe2 van der Waals heterostructures(vdWH). They are p-type semiconductors with indirect band gaps of 1.09 eV and 1.08 eV based on PBE functional respectively. By applying the external gate field, the PAs-WSe2 heterostructure would transform to the type-II band alignment from the type-I. With the increasing of magnitude of the electric field, two heterostructures turn into the n-type semiconductors and eventually into metal. Especially, PN/PAs-WSe2 vdWH are both high refractive index materials at low frequencies and show negative refractive index at high frequencies. Because of the steady absorption in ultraviolet region, the PAs-WSe2 heterostructure is a highly sensitive UV detector material with wide spectrum. The type-II PN-WSe2 heterostructure possesses giant and broadband absorption in the near-infrared and visible regions, and its solar power conversion efficiency of 13.8% is higher than the reported GaTe–InSe (9.1%), MoS2/p-Si (5.23%) and organic solar cells (11.7%). It does project PN-WSe2 heterostructure a potential for application in excitons-based solar cells.

Band Alignment Tailoring of InAs1−xSbx/GaAs Quantum Dots: Control of Type I to Type II Transition

Nano Letters ◽  
2010 ◽  
Vol 10 (8) ◽  
pp. 3052-3056 ◽  
Author(s):  
J. He ◽  
C. J. Reyner ◽  
B. L. Liang ◽  
K. Nunna ◽  
D. L. Huffaker ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Band Alignment ◽  
Type I ◽  
Type Ii

The electric field modulation of electronic properties in a type-II phosphorene/PbI2 van der Waals heterojunction

2019 ◽  
Vol 21 (15) ◽  
pp. 7765-7772 ◽  
Author(s):  
Yuting Wei ◽  
Fei Wang ◽  
Wenli Zhang ◽  
Xiuwen Zhang
Keyword(s):  
Solar Energy ◽  
Electric Field ◽  
Electronic Properties ◽  
External Electric Field ◽  
Van Der Waals ◽  
Optoelectronic Devices ◽  
Band Alignment ◽  
Type Ii ◽  
Direct Bandgap ◽  
Field Modulation

The 0.52/0.83 eV direct bandgap of P/PbI2 possesses a type-II band alignment, can effectively be regulated to 0.90/1.54 eV using an external electric field in DFT/HSE06, and is useful for solar energy and optoelectronic devices.

Highly-efficient heterojunction solar cells based on two-dimensional tellurene and transition metal dichalcogenides

2019 ◽  
Vol 7 (13) ◽  
pp. 7430-7436 ◽  
Author(s):  
Kai Wu ◽  
Huanhuan Ma ◽  
Yunzhi Gao ◽  
Wei Hu ◽  
Jinlong Yang
Keyword(s):  
Solar Cells ◽  
Transition Metal ◽  
Charge Separation ◽  
Transition Metal Dichalcogenides ◽  
Band Alignment ◽  
Type Ii ◽  
Two Dimensional ◽  
Heterojunction Solar Cells ◽  
Highly Efficient ◽  
Metal Dichalcogenides

Tellurene and TMDs show desirable type II band alignment for constructing highly-efficient heterojunction solar cells with strong charge separation and enhanced sunlight absorption.

Type I–type II band alignment of a GaAsSb/InAs/GaAs quantum dot heterostructure influenced by dot size and strain-reducing layer composition

2013 ◽  
Vol 46 (9) ◽  
pp. 095103 ◽  
Author(s):  
A Hospodková ◽  
M Zíková ◽  
J Pangrác ◽  
J Oswald ◽  
J Kubištová ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Gaas Quantum Dot ◽  
Layer Composition

Electrical Properties of n-GaN/p-SiC and n-AlGaN/p-SiC Heterojunction Diodes

2001 ◽  
Vol 693 ◽  
Author(s):  
B. Luo ◽  
J. Kim ◽  
R. Mehandru ◽  
F. Ren ◽  
K. P. Lee ◽  
...  
Keyword(s):  
Activation Energy ◽  
Band Alignment ◽  
Type I ◽  
Type Ii ◽  
Normal Type ◽  
Defect States ◽  
Dark Line ◽  
Continuous States ◽  
Line Defects ◽  
Heterojunction Diodes

AbstractProperties of n-GaN/p-SiC and n-AlGaN/p-SiC heterojunctions prepared by HVPE on 4H SiC substrates were studied by means of C-V, C/G-T, C-f, I-V and DLTS. It is shown, in agreement with earlier publications, that the GaN/p-SiC HJ is staggered type II with ΔEc=-0.4 eV andΔEv=0.6 eV. Whenchanging GaN for AlGaN with Al mole fraction of x=0.25-0.3 the band alignment becomes normal type I with ΔEc=0.2 eV andΔEv=0.6 eV. I-V characteristics of both heterojunctions bear evidence of strong tunneling via defect states, particularly centers with activation energy of 1.25 eV for GaN/4H SiC HJ. The tunneling was found to be more pronounced in the AlGaN/SiC HJs even though these HJs showed no evidence of formation of dark line defects at the interface, in contrast to GaN/SiC. DLTS measurements on both types of HJs revealed the presence of broad bands whose behavior is indicative of these bands being related to continuous states in the gap, most likely near the nitride/carbide interface.

Optical Investigation of the Band Offset of CdxZn1−xTe /ZnTe and ZnSexTe1−x/ZnTe Superlattices

1990 ◽  
Vol 198 ◽  
Author(s):  
Y. Rajakarunanayake ◽  
M. C. Phillips ◽  
J. O. Mccaldin ◽  
D. H. Chow ◽  
D. A. Collins ◽  
...  
Keyword(s):  
Valence Band ◽  
Band Alignment ◽  
Band Offset ◽  
Type I ◽  
Optical Investigation ◽  
Type Ii ◽  
Carrier Injection ◽  
Valence Band Offset ◽  
Small Component ◽  
Strained Layer Superlattices

ABSTRACTWe have analyzed photoluminescence spectra from CdxZnl−xTe /ZnTe and ZnSexTel−x/ZnTe strained layer superlattices grown by MBE, and obtained the band offsets by fitting to theory. We find that the valence band offset of the CdTe/ZnTe system is quite small (-50± 160 meV). In CdxZnl−xTe /ZnTe superlattices, the electrons and heavy holes are confined in the CdxZn1−xTe layers (type I), while the light holes are confined in the ZnTe layers (type II). On the other hand, the photoluminescence data from the ZnSexTe1−x /ZnTe superlattices suggest that the band alignment is type II, with a large valence band offset (−907 ± 120 meV). We also investigated the band bowing in the ZnSexTel−x alloys by optical spectroscopy, and found that there is only a small component of bowing in the valence band, while most of the bowing occurs in the conduction band. Based on our results for band alignments, we evaluate the prospects for minority carrier injection in wide bandgap heterostructures based on ZnSe, ZnTe, and CdTe.

A general method for type I and type II g-C3N4/g-C3N4 metal-free isotype heterostructures with enhanced visible light photocatalysis

2015 ◽  
Vol 39 (6) ◽  
pp. 4737-4744 ◽  
Author(s):  
Fan Dong ◽  
Zilin Ni ◽  
Peidong Li ◽  
Zhongbiao Wu
Keyword(s):  
Visible Light ◽  
Band Alignment ◽  
Visible Light Photocatalysis ◽  
Type I ◽  
Type Ii ◽  
Metal Free ◽  
General Method

Composite precursors were used to construct type I and type II g-C3N4/g-C3N4 metal-free isotype heterostructures based on different band-alignment patterns.

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