Prospective analysis of optoelectronic properties of ZnSnN2 for future tandem solar cells
Résumé
The nitrides of elements III such as AlxGayIn1-x-yN have been widely studied for optoelectronic applications and are of specific interest for solar cells. Unfortunately, made with indium, they will most likely suffer about the possible absence and / or increase of indium prices due to, for example, its use in flatscreen market. In this context, other alloys such as Zn-IV-N2 type II-IV nitrides have recently been suggested in which the element IV may be Sn, Ge or Si. The ZnSnN2 seems to have suitable properties and is composed of abundant and non-toxic elements. Studies on ZnSnN2 are nevertheless scarce and its properties are still poorly known. This work presents a first analysis of the optoelectronic properties of ZnSnN2. The films were made by sputtering and their stoichiometry was controlled to span from near-stoichiometric to excess zinc content. Advanced characterization techniques such as photoconductivity and absorption spectroscopies are used to obtain the optoelectronic response. Then, structural analyzes of the ZnSnN2 deposited on both glass and silicon substrates are done using Spectroscopy Raman and Atomic Force Microscopy. Finally, the band gap alignment is studied in situ during the growth process using an XPS setup connected under UHV to the deposition system.
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