Fermi level pinning or semiconductor electrodes in aqueous and non aqueous electrolytes: influence of the modification of the electrode surface

1989 ◽  
Vol 67 (3) ◽  
pp. 382-388 ◽  
Author(s):  
O. Savadogo
Keyword(s):  
Fermi Level ◽  
Acidic Medium ◽  
Open Circuit ◽  
Flat Band ◽  
Flat Band Potential ◽  
Fermi Level Pinning ◽  
Material Surfaces ◽  
Electrolyte Interface ◽  
Semiconductor Electrodes ◽  
Minority Carriers

Modification of several semiconductors material surfaces with H4SiW12O40•nH2O have been carried out to produce an increase in the open circuit photopotential at the semiconductor/electrolyte interface (Voc) without changing the flat-band potential. The augmentation of Voc is shown to be attributed to a decrease of the minority carriers recombination at the semiconductor/electrolyte interface along with the suppression of Fermi level pinning. The enhancement of Voc and the electrocatalytic activity of the hydrogen evolution reaction in acidic medium of the derivatized electrodes is attributed to the Fermi level unpinning. Keywords: photoelectrodes, photoelectrocatalysis, pinning, modification improvement.

Photoelectrochemical cells with n-CdTe

1982 ◽  
Vol 35 (10) ◽  
pp. 1949 ◽  
Author(s):  
AE Rakhshani ◽  
LE Lyons
Keyword(s):  
Fermi Level ◽  
Empirical Relationship ◽  
Open Circuit ◽  
Photoelectrochemical Cells ◽  
Flat Band ◽  
High State ◽  
Photovoltaic Properties ◽  
Minority Carrier Diffusion Length ◽  
Fermi Level Pinning ◽  
Redox Couples

The opto-electrical behaviour of single crystal n-type CdTe in aqueous solutions containing several redox couples Sn2+,4+, Fe2+3+ and Fe(CN)63-,4-in the dark and under irradiation is described. The minority carrier diffusion length was 0.13 μm from a combination of results on photocurrents and capacitance. The dopant concentration was 1.4 × 1017 cm-3 from Mott-Schottky plots. In the cdTe-Sn2+,4+ system the photovoltaic properties of the junction depended on the state of charge injection into the interface region. We distinguished between a 'high state' and a 'low state' where in the 'high state' both the open circuit photovoltage and the fill factor were approximately twice as large as in the 'low state'. Possibilities for a difference in the value of the built-in potential obtained from the photocurrent method and from a Mott-Schottky plot are described. The built-in potential (or the flat-band potential) was independent of the redox potential, an effect which is analogous to Fermi-level pinning. The empirical relationship between barrier height and band gap in a Fermi-level pinned junction held for our system.

Fermi-level pinning and effect of deposition bath pH on the flat-band potential of electrodeposited n-Cu2O in an aqueous electrolyte

2016 ◽  
Vol 253 (10) ◽  
pp. 1965-1969 ◽  
Author(s):  
F. S. B. Kafi ◽  
K. M. D. C. Jayathileka ◽  
R. P. Wijesundera ◽  
W. Siripala
Keyword(s):  
Fermi Level ◽  
Aqueous Electrolyte ◽  
Flat Band ◽  
Flat Band Potential ◽  
Fermi Level Pinning

Notizen: Fermi-Niveau und Flachbandpotential von Molekülkristallen aromatischer Kohlenwasserstoffe

1967 ◽  
Vol 22 (5) ◽  
pp. 843-844 ◽  
Author(s):  
Frank Lohmann
Keyword(s):  
Aromatic Hydrocarbon ◽  
Fermi Level ◽  
Electron Affinity ◽  
Ionization Energy ◽  
Flat Band ◽  
Flat Band Potential ◽  
First Approximation ◽  
Hydrocarbon Molecules

The sum of ionization energy and electron affinity for aromatic hydrocarbon molecules is constant and therefore the Fermi level for intrinsic aromatic hydrocarbon crystals is in first approximation independent of the nature of the hydrocarbon. This relationship leads in turn to a constant value for the flat band potential of aromatic hydrocarbon crystals in contact with an electrolyte. An estimate of this value is given.

scholarly journals Improving organic photovoltaic cells by forcing electrode work function well beyond onset of Ohmic transition

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chao Zhao ◽  
Cindy G. Tang ◽  
Zong-Long Seah ◽  
Qi-Mian Koh ◽  
Lay-Lay Chua ◽  
...  
Keyword(s):  
Solar Cells ◽  
Fermi Level ◽  
Work Function ◽  
Organic Solar Cells ◽  
Carrier Mobility ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Fermi Level Pinning ◽  
Electrode Contact

AbstractAs electrode work function rises or falls sufficiently, the organic semiconductor/electrode contact reaches Fermi-level pinning, and then, few tenths of an electron-volt later, Ohmic transition. For organic solar cells, the resultant flattening of open-circuit voltage (Voc) and fill factor (FF) leads to a ‘plateau’ that maximizes power conversion efficiency (PCE). Here, we demonstrate this plateau in fact tilts slightly upwards. Thus, further driving of the electrode work function can continue to improve Voc and FF, albeit slowly. The first effect arises from the coercion of Fermi level up the semiconductor density-of-states in the case of ‘soft’ Fermi pinning, raising cell built-in potential. The second effect arises from the contact-induced enhancement of majority-carrier mobility. We exemplify these using PBDTTPD:PCBM solar cells, where PBDTTPD is a prototypal face-stacked semiconductor, and where work function of the hole collection layer is systematically ‘tuned’ from onset of Fermi-level pinning, through Ohmic transition, and well into the Ohmic regime.

scholarly journals n-GaAs Band-Edge Repositioning by Modification with Metalloporphyrin/Polysiloxane Matrices

2003 ◽  
Vol 26 (1) ◽  
pp. 11-21 ◽  
Author(s):  
Hikmat S. Hilal ◽  
Moayyad Masoud ◽  
Samar Shakhshir ◽  
Najeh Jisraw
Keyword(s):  
Solar Energy ◽  
Polymer Matrix ◽  
Dark Current ◽  
Open Circuit Potential ◽  
Open Circuit ◽  
Flat Band ◽  
Flat Band Potential ◽  
Oxygen Production ◽  
Onset Potential ◽  
Photo Current

Tetra(-4-pyridyl)porphyrinatomanganese(III)sulfate,MnP, (in the forms ofMnIIIandMnIImixture), was embedded into a polysiloxane polymer matrix and attached to the surfaces ofn-GaAs wafers. The n-GaAs/polymer/MnPsystem was annealed under nitrogen and used for photoelectrochemical study in water/LiCIO4/Fe(CN)63-/Fe(CN)64−system. The results indicated a positive shift in the value of the flat-band potential of the semiconductor due toMnP. This was manifested by shifting the values of the dark-current onset potential and the photo-current open-circuit potential towards more positive values. These findings are potentially valuable in future applications of solar energy in hydrogen and oxygen production from water.

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