Low-Pollution and Controllable Selective-Area Deposition of a CdS Buffering Layer on CIGS Solar Cells by a Photochemical Technique

Abstract

A chemical-bath deposition method has recently been applied for the industrial deposition of CdS buffer layers in high-efficiency Cu(In, Ga)Se2 (CIGS) solar cells; however, its massive raw material waste and heavy pollution have also hindered its long-range industrialization. In this study, a type of low-pollution and controllable selective-area deposition of CdS thin films on cells was proposed and conducted by a photochemical deposition (PCD) technique using an aqueous solution containing S2O32–, SO32–, and Cd2+. The as-deposited films are low-crystallinity, uniform, and compact with thicknesses of 30–50 nm. Moreover, the depositions of CdS thin films were further investigated by tuning the deposition time, absorption of cadmium ions, sulfur concentration, and light intensity. Additionally, an ion-by-ion mechanism was proposed for the growth of CdS thin films by a PCD technique. Furthermore, the optimal CdS thin layer was applied in CIGS solar cells, which showed a high efficiency of 10.45%. This research would give new insight into the efficient deposition of CdS thin films on solar cells with low pollution.