Effect of sulfurization temperature on optical and compositional properties of sputtered Zn(O, S) thin films

Abstract

Zinc oxysulfide or Zn(O,S) is emerging as an alternate n-type buffer layer for kesterite, chalcogenides and CdTe based thin film solar cell due to it is being made from non-toxic elements and tunable bandgap, its suitable optical and electrical properties required for a buffer layer. Generally, buffer layers of these solar cells are deposited using chemical bath deposition (CBD) techniques, but these require breaking of vacuum and again inserting the sample in vacuum during solar cell fabrication, which is not economical and is cumbersome. Sputtering is considered to be industrial process and therefore, here we have deposited Zn(O,S) thin film by sputtering technique and effect of sulfurization temperature on bandgap and composition of Zn(O,S) films have been studied. The bandgap of deposited films changed from 3.36 eV to 3.15 eV by changing the sulfurization temperatures. By changing the sulfurization temperature, the composition of films also changed. Crystallite size (D) of Zn(O,S) films increased from 12.1 nm to 22.3 nm by varying the sulfur content for samples S1-S4, respectively. Optical, morphological, compositional and structural properties have been studied using UV-Vis-NIR spectroscopy, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffractometer (XRD), respectively.