A low cost and single source atmospheric pressure vapor phase epitaxy of ZnS for thin film photovoltaic applications

A novel and low cost vapor phase epitaxy (VPE) method using a single non-volatile source has been used to deposit ZnS thin films on soda lime glass substrates. Utilization of the non-volatile source eliminates the need for expensive and sophisticated reactors commonly used in conventional VPE. Instead, this experiment was carried out using inexpensive and easily attainable apparatus. The vapor phase reaction process described is also more compatible to the industry standard dry deposition processes of the other layers in the thin film solar cell stack for Cu(In,Ga)Se2 (CIGS), Cu2ZnSnS4 (CZTS) and CdTe photovoltaic (PV) devices. In this experiment, the substrate temperature was varied from 400 to 480 °C and the ZnS thin films produced were analyzed using X-ray diffractometry (XRD), optical spectroscopy, field emission scanning electron microscope (FESEM) and Hall effect measurement system. The films were found to be hexagonal structured except for the film deposited at 480 °C, where the film was found to be cubic. The thickness, bandgap and resistivity of the deposited films ranged from 54 to 351 nm, 3.18 to 3.83 eV and 2 × 103 to 1.6 × 104 Ω·cm respectively.