Secondary phases and temperature effect on the synthesis and sulfurization of CZTS

•Copper, Zinc and Tin sulfides were synthesized by solution method employing Na2S as sulfur source.•Structural, optical and morphological analysis indicated major portion of CZTS.•Secondary phases such as SnS2, SnS and Cu3SnS4 at 350° and 450 °C.•Secondary phases vanishing significantly at 550° and 650 °C.•High absorption coefficient for CZTS in the range of 104–105 cm−1.•Electrochemical analysis supported that the CZTS samples could be used as absorber material in thinfilm solar cells.