Charge Transfer from PbS Quantum Dots to Insulating TiO2 Matrix

1995 ◽  
Vol 382 ◽  
Author(s):  
R. Könenkamp ◽  
P. Hoyer
Keyword(s):  
Conduction Band ◽  
Quantum Confinement ◽  
Visible Spectrum ◽  
Spatial Separation ◽  
Band Alignment ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Carrier Transfer ◽  
Quantum Size ◽  
Pbs Quantum Dots

ABSTRACTWe report on the photoconductivity of thin films consisting of a porous nanocrystalline TiO2 matrix and quantum size PbS clusters adsorbed on the inner surfaces of theTiO2. The PbS clusters are typically a few nm in size and are not connected. Due to quantum confinement the bandgap of the clusters is widened to around 2 eV from the 0.41 eV value for PbS bulk. The clusters thus absorb in the visible spectrum. However, due to their spatial separation, photoconductance through the film requires carrier transfer through the TiO2 matrix. Our data show this to occur only for clusters <25 Å, for which the conduction band edge lies above the TiO2 conduction band edge. For larger clusters the band alignment at the TiO2/PbS interface appears to be unfavorable for carrier transfer; these clusters do not contributeto photoconduction.

BAND ALIGNMENT FOR AMBIPOLAR-DOPING OF PbxZn1-xTe ALLOYS: A FIRST-PRINCIPLE STUDY

2012 ◽  
Vol 26 (07) ◽  
pp. 1150041 ◽  
Author(s):  
XIAO-JUAN YUAN ◽  
JIAN-ZHE LIU ◽  
YONG ZHANG ◽  
LI-MING TANG
Keyword(s):  
Conduction Band ◽  
State Of The Art ◽  
Spectral Response ◽  
Optoelectronic Devices ◽  
Solar Spectrum ◽  
Band Alignment ◽  
Band Gaps ◽  
Band Edge ◽  
Conduction Band Edge ◽  
First Principle

Using a first-principle band-structure method and a special quasirandom structure (SQS) approach, we present state-of-the-art HSE06 functional calculations for demonstrating the possibility of ternary PbxZn1-xTe alloys to be bipolar-doping materials. The results show that the bowing parameters and the band gaps of these alloys sensitively depend on the composition x. Due to the full overlapping and delocalization, the coupling between Pb outermost p orbits and Zn 4s orbits become very strong, thus resulting in a significant downshift of conduction band edge with the increase of Pb concentration x. When the concentration x reaches 0.25, it is demonstrated that the Pb0.25Zn0.75Te alloy has a substantial decrease in the conduction band edge, while leaving the valence band edge almost unchanged compared to that of binary ZnTe, thus improving the possibility for ambipolar-doping. Meanwhile, the spectral response of this alloy (Eg = 1.38 eV) is very consistent with the solar spectrum. We expect that our results will be helpful for the applications of optoelectronic devices.

scholarly journals Conduction Band Edge Energy Profile Probed by Hall Offset Voltage in InGaZnO Thin Films

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 822
Author(s):  
Hyo-Jun Joo ◽  
Dae-Hwan Kim ◽  
Hyun-Seok Cha ◽  
Sang-Hun Song
Keyword(s):  
Magnetic Field ◽  
Electron Density ◽  
Conduction Band ◽  
Electron System ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Offset Voltage ◽  
Three Samples ◽  
Dimensional Electron System ◽  
Longitudinal Distance

We measured and analyzed the Hall offset voltages in InGaZnO thin-film transistors. The Hall offset voltages were found to decrease monotonously as the electron densities increased. We attributed the magnitude of the offset voltage to the misalignment in the longitudinal distance between the probing points and the electron density to Fermi energy of the two-dimensional electron system, which was verified by the coincidence of the Hall voltage with the perpendicular magnetic field in the tilted magnetic field. From these results, we deduced the combined conduction band edge energy profiles from the Hall offset voltages with the electron density variations for three samples with different threshold voltages. The extracted combined conduction band edge varied by a few tens of meV over a longitudinal distance of a few tenths of µm. This result is in good agreement with the value obtained from the analysis of percolation conduction.

Size-Dependent Valence and Conduction Band-Edge Energies of Semiconductor Nanocrystals

ACS Nano ◽  
2011 ◽  
Vol 5 (7) ◽  
pp. 5888-5902 ◽  
Author(s):  
Jacek Jasieniak ◽  
Marco Califano ◽  
Scott E. Watkins
Keyword(s):  
Conduction Band ◽  
Semiconductor Nanocrystals ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Size Dependent

scholarly journals Photocatalytic properties of a new Z-scheme system BaTiO3/In2S3 with a core–shell structure

RSC Advances ◽  
2019 ◽  
Vol 9 (20) ◽  
pp. 11377-11384 ◽  
Author(s):  
Kaili Wei ◽  
Baolai Wang ◽  
Jiamin Hu ◽  
Fuming Chen ◽  
Qing Hao ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Valence Band ◽  
Conduction Band ◽  
Shell Structure ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Core Shell ◽  
Valence Band Edge ◽  
Core Shell Structure ◽  
Positive Valence

It's highly desired to design an effective Z-scheme photocatalyst with excellent charge transfer and separation, a more negative conduction band edge (ECB) than O2/·O2− (−0.33 eV) and a more positive valence band edge (EVB) than ·OH/OH− (+2.27 eV).

Experimental observation of quantum confinement in the conduction band of PbS quantum dots

2013 ◽  
Vol 42 (4) ◽  
pp. 197-200 ◽  
Author(s):  
I. N. Demchenko ◽  
M. Chernyshova ◽  
X. He ◽  
R. Minikayev ◽  
Y. Syryanyy ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Experimental Observation ◽  
Conduction Band ◽  
Quantum Confinement ◽  
Pbs Quantum Dots

ALD Deposited Al2 O3 Films on 6H-SiC(0001) after Annealing in Hydrogen Atmosphere

2005 ◽  
Vol 483-485 ◽  
pp. 559-562 ◽  
Author(s):  
Kun Yuan Gao ◽  
Thomas Seyller ◽  
Konstantin V. Emtsev ◽  
Lothar Ley ◽  
Florin Ciobanu ◽  
...  
Keyword(s):  
Conduction Band ◽  
Photoelectron Spectroscopy ◽  
Depth Profiling ◽  
Atomic Layer ◽  
Hydrogen Atmosphere ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Strong Increase ◽  
Admittance Spectroscopy ◽  
Spectroscopy Measurement

Atomic Layer Deposited Al2O3 films on hydrogen-terminated 6H-SiC(0001) were annealed in hydrogen atmosphere and characterized by admittance spectroscopy measurement and photoelectron spectroscopy (PES). The resultant density of interface trap (Dit) from admittance spectroscopy measurement is reduced near mid gap, but increases strongly towards the conduction band edge. Systematic PES measurements show that hydrogen annealing introduces Si4+ as a new component besides Si0 and Si+. Using different electron escape depths for photon electrons, depth profiling of Si in its different oxidation states was performed. The result indicates the formation of a top SiO2 layer and a rougher interfacial layer containing more Si+ and Si4+ which could be responsible for the strong increase of Dit just below the conduction band edge.

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