| AVS 58th Annual International Symposium and Exhibition | |
| Energy Frontiers Focus Topic | Wednesday Sessions |
| Session EN1+TF-WeA |
| Session: | Thin Film Chalcogenide Solar Cells (CIGS, CZTS, CdTe and Related Materials) |
| Presenter: | Parag Vasekar, The State University of New York at Binghamton |
| Authors: | P. Vasekar, The State University of New York at Binghamton L. Ganta, The State University of New York at Binghamton D. Vanhart, The State University of New York at Binghamton T. Dhakal, The State University of New York at Binghamton C.R. Westgate, The State University of New York at Binghamton |
| Correspondent: | Click to Email |
Thin film solar cells based on Cu(In,Ga)(S,Se)2 and CdTe have demonstrated significant improvement in last few years and they are also being transferred to production level. However, both CIGS and CdTe based thin film solar cells are hindered by potential environmental hazard issues and scarcity issues associated with the constituent elements , mainly Te, In, Ga and to some extent Se. Recent research trends are moving towards finding alternatives based on earth-abundant and non-toxic elements. An alternative material Cu(Zn,Sn)(S,Se)2 is being explored these days by the thin film photovoltaics community which contains earth abundant materials like Zn and Sn. CZTS structure can be derived from CuInS2 chalcopyrite structure by replacing one half of the constituent indium atoms by zinc and other half by tin. The resulting bandgap varies in the range of 0.8 eV for a selenide structure to 1.5 eV for a sulfide structure. Copper and sulfur in earth’s crust are 50 and 260 ppm respectively and while abundance of zinc and tin is 75 and 2.2 ppm in respectively. As compared to this, indium in earth’s crust is 0.049 ppm and selenium 0.05 ppm. CZTS also has a large absorption coefficient in the order of 104 cm−1. There are vacuum-based as well as non-vacuum based approaches for the synthesis of CZTS solar cells. Among vacuum based approaches, generally sulfurization in H2S atmosphere is carried out on sputtered CuZnSn precursors. However, there are toxicity issues involved with the use of H2S gas. We subscribe to the philosophy of sticking to a non-toxic approach of synthesizing thin film solar cells and for the first ever time introduced a non-toxic sulfur precursor called di-tertiray-butyl-disulfide (TBDS) for the sulfurization of CZT layer. Initial results are quite encouraging and device quality CZTS cells are already being synthesized. The CZTS cells are characterized using materials characterization techniques such as SEM, XRD, XPS and photovoltaic parameters are being extracted under AM 1.5 conditions and also analyzed using quantum efficiency measurement. This is the very first attempt to successfully synthesize CZTS solar cells using a non-toxic sulfur source.