Temperature-assisted mechanochemically synthesized Cu and In doped SnS nanoparticles for thin film photovoltaics: Structure, phase stability and optoelectronic properties

This work reports the phase stability and optoelectronic studies of undoped, Cu and In doped SnS nanoparticles prepared by temperature-assisted mechanochemical reaction. Initially, single-phase formation of orthorhombic structured SnS is attained by tailoring Sn:S weight ratio and heating rate through Raman and XPS analyses. Undoped SnS exhibits direct energy band gap -1.42 eV, resistivity -252,000 LI cm and hole concentration -1013 cm-3. Further, without affecting the chemical structure of SnS, optoelectronic properties are enhanced with the substitutional doping of Cu2+ and In3+ into SnS which is achieved with doping up to 4%. Raman studies indicated the formation of phase pure SnS nanoparticles for In doped samples whereas secondary phases are formed by increasing the Cu doping above 4%. Among all dopants, Cu 4% doped SnS exhibits ptype conductivity with band gap 1.01 eV and having improved electrical resistivity -2300 LI cm and carrier concentration -1016 cm-3.