Dear Abdellah

Attached please find a file about detailed calculation method for VB and CB of semiconductors along with the required data..

X-ray or ultraviolet photoelectron spectroscopy can give us the valence band maxima (or HOMO). When combined with UV-Vis spectroscopy for band gap estimation, we can get the conduction band minima. Alternatively, if possible, cyclic voltametry can also give us the redox potentials (in-principle, it is the same information, but of course the presence of an electrolyte may complicate the data interpretation).

Correct, UVP and Cyclic voltammetry can be used for band gap and band position. UV vis can be used for obtainment of band gap. DFT can also be used for obtainment of band position through simulation.

How about using Mott-Schottky analysis. It is, in general, used to determine the flat-band potential of a semiconductor and the carrier density. Using the typical relations one can find out the VB and CB edge positions. Please go through the theoretical aspects of it.

cyclic voltmetery can be used for LUMO and HOMO determination. In CV curve, Oxidation potential and Reduction potential are HOMO and LUMO of semiconductor.

how far theoretically calculated band edge positions and practically synthesised material's band edge positions vary. what is the significance in difference, if in case. please give some reference for theoretical & practical calculations

Mott-Schottky plots can directly tell about the position of the flat-band potentials. Unfortunately such a technique needs care and is not easy to do. 

I would also advise you to use values of open circuit potential and the redox potential of the redox couple. Combined you may use then find vale of flat band position (band edges). Think of those.

Theoretically the valence band edge potential (Evb) and the conduction band edge potential (Ecb) of semiconductor material can be calculated by using the following equation:

Evb = χ - Ee+0.5Eg

Ecb = Evb + Eg

Where, is the valence band edge potential,

χ is the absolute electronegativity of the semiconductor, which is determined as the geometric mean of the electronegativity of the constituent atoms,

Ee is the energy of free electrons on the hydrogen scale (4.5 eV) and

Eg is the band gap energy of the semiconductor.

@Santhosh Kumar

Does the formula you stated here applies to doped semiconductors also? In such case how to find out the absolute electronegativity of the semiconductor and energy of the free electrons?

Dear Santosh Kumar

The energy of free electrons on the hydrogen scale is equal 4.5 eV or -4.5 eV 

and it is used for all compounds 

thanks

Does anyone have a reference concerning to this determination?

Dear Santosh Kumar ,

If possible, How can I determine the absolute electronegativity χ of

 mixed oxides formulated as A1-xB1-xCxO3?

 how to calculate absolute electronegativity of doped semi conductor? 

 @ Abhilash Sugunan, can you please tell me how we can calculate the valence band maxima (or HOMO) by X-ray photoelectron spectroscopy. can u give us the reference or procedure please.

Here you can find good explanation and band gap calculator,

http://www.instanano.com/characterization/theoretical/uv-vis-spectroscopy-band-gap-calculation/

The energy band configuration of photocatalysts has crucial effect on their properties, such as the wavelength of excitation, redox ability of the photogenerated holes and electrons, and the separation efficiency of the charge carriers. These energies are estimated by applying the Mullikan electronegativity theory for atoms using Eqs. (1) and (2) :

EVB = X – Ee +  ‏0.5Eg      (1)                                                                                                           

ECB = EVB − Eg                                                                                                                    (2)

In which EVB and ECB present valence band (VB) and conduction band (CB) edge potentials, respectively; Ee is the energy of free electrons on the hydrogen scale ca. 4.50 eV; χ is electronegativity of the semiconductor expressed as the geometric mean of the absolute electronegativity of the constituent atoms. For more information, please refer to the attached paper.

Hi Dear Aziz Habibi-Yangjeh,

I saw your document, can I write the number of atoms into fractions?, because my compounds are formulated as A1-xB1-xCxO3.

Dear Abdellah

Attached please find a file about detailed calculation method for VB and CB of semiconductors along with the required data..

Thank you so much Dear Aziz Habibi-Yangjeh,

Dear Abdellah 

You are welcome.

Dear Dr. Aziz 

How I can calculate the X electronegativity for 25% ZnO/xTiO2-SiO2 (x = 0, 10, 15, 20 wt%) tri-composite.  where I calculate Eg for samples from Tauck equation 

The direct band gap energy (Egap) of catalysts is 4.64 eV, 4.64 eV, 4.86 eV, and 4.88 eV for Zn/10Ti-SiO2, Zn/15Ti-SiO2, Zn/SiO2 and Zn/20Ti-SiO2; respectively.

The preparation method is: Ti-SiO2 composites of Ti molar ratios 0, 10, 15 and 20 % were synthesized by the sol-gel method. Tetraethyl orthosilicate (TEOS, 98% Aldrich) and titanium isopropoxide (TIP, 97% Aldrich) were used as the SiO2 and TiO2 sources respectively. Zn+2 ions of 25 wt% were doped on the photo-catalysts using zinc nitrate hexahydrate (Zn(NO3)2. 6 H2O, 98% Aldrich) by the wet impregnation method, dried overnight at 100 °C and calcined at 540 °C with a heating ramp of 1°C.

Thank You Dear Aziz Habibi-Yangjeh sir . The attached PDF file by you is very clear and easy to determine the Xc (electronegativity) value for a photocatalyst.

Dear Dr. Yagna PRAKASH Bhoi

That is nice of you.

Dear AZIZ,

i am also working in g-C3N4. In my calculation i got conducion band energy is 0.97eV but in your reference you got -1.13eV. how is possible. because we both are got same bandgap like 2.68eV in my case. Are you consider the g- in equation. for XC3N4 calculation i used only carbon and nitrogen. did you consider the g also if yes please give the electron affinity and first ionization energy of "g".

Could you tell me whether my calculation is right or wrong?

I am also suggest Cyclic voltametry technique

Dear Prof. Aziz,

The values of electron affinity in the attached file is different than that in the following link, please advise

http://www.rsc.org/periodic-table?fbclid=IwAR1DKk1WrSg5c4A0-YN8kvk9M_Stxgetf9rzgpdWuRh--DoaPW2AJd4e8Lc

Would you mind to tell me the Fermi energy calculation of semiconductors?

Dear Vishwanathan,

The more used method in the literature for the evaluation of valence band and conduction band energy is the MS plot analysis. You just need to perform Electro impedance spectroscopy EIS of your samples at different frequencies and then plot the MS plot, you will get the desired result. You can go through this article.

https://pubs.acs.org/doi/pdf/10.1021/ed084p685?rand=vtqgjb63

Regards,

Chandan