Dear S. Khademinia,

It depends on your materials. Generally, there are two ways:

1. Directly from the DRS spectra, or

2. Using Kubelka-Munk function 

Please follow the attached articles.

Dear Shahin

You can calculate band gap using DRS spectrum by Kubelka-Munk function for direct band gap semiconductors:

                                                            [F (R∞)hν]2= C(hν − Eg)     

Hope, it helps you.

Prashant                              

Thank you so much for the formula. I attached a file for you. Is it possible to include the formula in excel file to calculate the band gap.

Thank you so much

Dear S. Khademinia,

It depends on your materials. Generally, there are two ways:

1. Directly from the DRS spectra, or

2. Using Kubelka-Munk function 

Please follow the attached articles.

how can we identify if the prepared semiconductor has a direct or indirect transition?

Here you can find good explanation and band gap calculator,

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

It was really good explanation sir, thank for the information