If a material have both direct and indirect band gap. If this material is used in the solar cell or photo detector application. Then how can we know which band gap is used for exciton generation?
Dear Brajesh,
The most optical property for the operation of the solar cells and photo detectors is the absorption coefficient curve as a function of the incident electromagnetic radiation wavelength lambda. This curve depends on the energy band structure.
When the material has direct bandgap then the rate of increase of the alpha with decrease in the wavelength after crossing the cut off wavelength corresponding to the energy gap, will be large while it will be smaller in case of indirect bandgap material.So,from the shape of the alpha versus lambda curve you can identify the type of the band gap and its energy.
Best wishes
maybe the references mentioned in https://www.researchgate.net/post/What_is_the_best_experimental_method_for_calculating_of_the_band_gap_of_a_semiconductor_material_what_is_it_based_on
can be of your help.
Hi, you migth make a X-ray photoelectron spectroscopy (XPS) study.
This mensurits may determine density of the electronic states in the material as wel as overall electronic structure, and elementary analises.
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