I am trying to make CZTS thin film however its bandgap is coming more than 2eV.What are the possible reasons for this?I had annealed the film at 350C.
1.What are the possible phases that cause this high band gap?
2.CZTS can be formed below 500C annealing temperature or not?
3. soda lime glass will degrade at temperature around 500C orit can sustain.
Hi Goutam
The possible secondary phases that can appear in the CZTS system are ZnS, CuS, Cu2SnS3, and Sn2S. I think you can are gettng large value for the band gap because of the presence of ZnS as secondary phase. It have large band gap value so it can appear as insulator reducing the CZTS content. You can refer to these papers for further information.
Answer to
Q.1 Look at the Ternary Phase diagram of CZTS. You can get a better idea.
Q.2 Most of the literature say an optimum annealing temperature of 550 deg.C.
Q.3 Soda lime glass sustains at that T (550 deg.C).
http://www.intechopen.com/books/solar-cells-research-and-application-perspectives/thin-film-solar-cells-using-earth-abundant-materials
Thanks kunal
I have one more doubt that CZTS is formed at higher annealing temperature>500C. HOwever on SLG this is difficult. also is there any other mean of calculating Band gap of CZTS (other than UV-VIS). How do we confirm that CZTS is formed.
Goutam,
You can go for ellipsometery measurements which will give you more accuracy in determining the band gap value.
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