Achieving desired quality of ZnS buffer layer by optimization using air annealing for solar cell applications

The possibility of maximum transmittance at lower thickness of light transmitting ZnS layer and its optimization by air-annealing as an alternative to hazardous and expensive CdS is reported in this communication in order to achieve better buffer layer for solar cells. Thin films of ZnS were deposited using e-beam evaporation on glass and ITO substrates and subjected to air-annealing followed by characterizations for physical properties. XRD patterns revealed amorphous behavior which transformed into cubic (111) plane with change of substrate and annealing whereas surface topography reveals hill and deep valley like structures. Optimal transmittance of maximum 95% in visible region, direct band gap of 3.38 eV and maximum electrical conductivity were observed for 200 °C annealed films. The study refers that films annealed at 200 °C are claimed to be suitable for buffer layer applications.