Fabrication of $\hbox {Cu}_{2}\hbox {ZnSn(S,Se)}_{4}$ thin film solar cell devices based on printable nano-ink

Abstract

$\hbox {Cu}_{{2}}\hbox {ZnSnS}_{{4}}$ (CZTS) as a promising light-absorber material has been extensively applied in photovoltaic solar cells due to its huge absorption coefficient (${\sim }10^{4}\, \hbox {cm}^{-1})$ and optimal bandgap (${\sim }\hbox {1.5 eV}$). In this study, stable and printable CZTS nano-ink was acquired by dispersing CZTS nanocrystals (NCs) in organic solutions. The kesterite CZTS NCs possess uniform size and good crystallinity. The Raman peak of CZTS is located at $330\, \hbox {cm}^{-1}$, which illustrates that the NCs consist of single-phase CZTS without any impurities. The as-prepared CZTS nano-ink was in turn spin-coated onto the Mo substrate to obtain the desired CZTS thin films under the conditions of anti-vacuum. The compact and dense CZTSSe absorbers were acquired by sulphuring and selenizing the as-prepared thin films. The band gap of the photovoltaic absorber materials is 1.2 eV after incorporating Se into the photovoltaic thin films. Finally, the CZTSSe photovoltaic thin film device, whose power conversion efficiency was $1.40\pm 0.14\%$, was prepared by this easy and green method.