Sol-gel processed Cu2ZnSnS4 thin films for a photovoltaic absorber layer without sulfurization

Abstract

Sol-gel processed Cu2ZnSnS4 (CZTS) thin films were fabricated without sulfurization for application as a photovoltaic absorber layer. The precursor solution was made from CuCl2, Zn(ac)(2), SnCl2, thiourea, and 2-methoxyethanol and the spin-coated film was annealed at temperature above 500 A degrees C under a N-2 atmosphere. A homogeneous and compositionally uniform film with single CZTS phase was obtained. Film composition featuring larger grains, which is desirable in photovoltaic cells, was obtained with heat treatment at 540 A degrees C. The grain size was up to 1 mu m and the Cu/(Zn + Sn) and Zn/Sn ratios were 0.93 and 1.07, respectively and the band gap energy was 1.56 eV.