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

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. - Highlights: • 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 and 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