A comparative study of Cu2ZnSn(SxSe1-x)4 nanoparticles for solar cells: From chemical synthesis to devices

Thin-film solar cells using quaternary compounds Cu2ZnSn(SxSe1-x)(4) (0 <= x <= 1; CZTSe, CZTSSe, or CZTS) as absorber materials have attracted a lot of attention from the photovoltaic research community. Traditionally, vacuum-based techniques have been used for the synthesis of Cu2ZnSn(SxSe1-x)(4) absorbers. In this work, an easy, less toxic, non-vacuum, single-reaction chemical route is used for the synthesis of Cu2ZnSn(SxSe1-x)(4) (x = 0.0,0.4,1.0) nanoparticles. Using structural characterization techniques, the presence of kesterite phase in the as-synthesised nanoparticles is confirmed. The surface micrographs revealed increase in nanoparticle grain size with the selenium doping and nearly stoichiometric composition with compact morphology of nanoparticles. Further, the optical characterization of as-synthesised nanoparticles exhibited bandgaps in the range 1.52 - 1.02 eV which are optimal for thin film solar cell applications. The fabricated solar cells using synthesised compounds exhibited promising photo response capabilities with a highest efficiency of 0.752% for Cu2ZnSn(S0.4Se0.6)(4) absorber-based device under AM1.5 illumination without any buffer layer. Results presented in this work indicate the suitability of the kesterite compounds synthesized through the chemical route as absorber materials for cheap solar cells.