Cu2ZnSnS4 thin films by simple replacement reaction route for solar photovoltaic application

• Pure kesterite Cu2ZnSnS4 thin films deposited by replacement reaction route
• Energy band gap of films is 1.45 eV.
• p-type films with conductivity of 4.6 S/cm & mobility of 1.4 cm2 S− 1 V− 1
• Fabrication of Graphite/Cu2ZnSnS4/CdS/ZnO/SnO2:In/Glass solar cell
• Solar cell delivered efficiency of 6.17% with high fill factor of 0.62

A process for deposition of Cu2ZnSnS4 (CZTS) films using replacement of Zn2 + in ZnS is demonstrated. X-ray diffraction pattern and Raman spectroscopy confirm the formation of pure CZTS. Atomic force microscopy shows the films to be homogeneous and compact with root mean squared roughness of 6 nm. The direct band gap of CZTS films as elucidated by UV–Vis-NIR spectroscopy is 1.45 eV. The CZTS films exhibit p-type conduction with electrical conductivity of 4.6 S/cm. The hole concentration and hole mobility is determined to be 3.6 × 1017 cm− 3 and 1.4 cm2V− 1 s− 1 respectively. Solar cells with structure: graphite/CZTS/CdS/ZnO/SnO2:In/Soda lime glass are also fabricated, gave photo-conversion efficiency of 6.17% with open circuit voltage and short circuit current density of 521 mV and 19.13 mA/cm2, respectively and a high fill factor of 0.62. The external quantum efficiency of the solar cell lies above 60% in the visible region.