Alternative back contacts in kesterite Cu2ZnSn(S1-xSex)4 thin film solar cells

Molybdenum (Mo) is the most used back contact in Cu2ZnSn(S1-xSex)(4) based solar cells. However, it has been suggested recently that Mo is not stable at the interface with Cu2ZnSn(S1-xSex)(4). In addition, to the best of our knowledge, no experimental study has been carried out so far to test whether solar cells built on another back contact could exhibit better photovoltaic properties. For this purpose, various metals (Au, W, Pd, Pt, and Ni) are deposited on top of Mo, and it is demonstrated that it is possible to synthesize device-quality Cu2ZnSn(S1-xSex)(4) thin films on W, Au, and Pt back contacts. It is shown that that W and Au back contacts allow enhancing the photogenerated current, but that Mo remains the best back contact in terms of power conversion efficiency. (C) 2014 AIP Publishing LLC.