Question

Which instrument used to measure band gap of a material?

Answer 1

Both above methods work, I would add that using UV-vis data can be tricky because many different equations to extract Eg from the data exist that may or may not be sensitive to defect absorption and scattering at low energies. Also, unless the plots are very linear, the fits to find the x-intercept are not that accurate, i.e. depending on where exactly you fit the data Eg can vary up to 0.5eV.

I think the most reliable can be photoluminescence. It requires sufficient yield and the knowledge that it is mainly band-to-band transitions that luminesce, but if that is clear the analysis is simple - the peak position is the band gap. It also gives you a convenient method to monitor recombination which I assume you're interested in since CZTS is usually researched for solar cells.

Answer 2

Hi,
=======:
Here is your answer,
=======:
The best tool for measuring the bandgap of solid samples is Uv-visible diffuse reflactence spectroscopy. More than one maxima's in the PL analysis are always confusing. Covert %R data to kubelka-Munk, F(R), and use the relation (F(R) *hv)n vs hv.

=======
HOPE YOU WILL UNDERSTAND MY WORDS, a request is here please as I am an ACE ranker I wish that to make my way easy for the GENIUS rank you should mark my answer brainlest if you wish then only ☺.
=======