Photoactive sulfide materials typically under-perform with respect to their theoretical maximum photovoltaic efficiency compared to other light absorbing solids. In an effort to reveal the underlying cause of this situation, we investigate several potential back contact metals for photovoltaic devices using the principles of band alignment; principles that have repeatedly shown to be of key importance in this field. Specifically, the sulfides SnS, CuInS2 and Cu2ZnSnS4 are studied in contact with the metals Mo, Sn, Ti, W and Zr and their common terminations. We also consider the stability with respect to interfacial chemical degradation and show that almost all systems used to date are likely to form interstitial two-dimensional metal disulfides at the heterojunction interface. The likely effects of these disulfide secondary phases are explored and the optimal configurations for each photoactive sulfide presented.
Bibliographical noteFunding Information:
LAB is an International Research Fellow of the Japan Society of Promotion of Science (JSPS) (grant number 26.04792). This work was also supported by a Grant-in-Aid for Young Scientists (A) (grant No. 15H05541) and Scientific Research (B) (grant No. 15H04125) from JSPS and MEXT Elements Strategy Initiative to Form Core Research Center. The computing resources of ACCMS at Kyoto University were used in this work.
© 2017 The Royal Society of Chemistry.