Transparent ZnTe:Cu contacts for bifacial characterization of CdTe solar cells

Abstract

AbstractCu-doped ZnTe films grown by galvanic deposition were developed to provide transparent ohmic contacts to CdTe solar cells. Control of the Cu doping with triethanolamine was critical to limit the free Cu in order to achieve high transparency (>60% in the visible) and to minimize shunting. Devices with ZnTe:Cu contacts had comparable performance to devices with Cu/Au or Cu/graphite contacts, achieving Voc of 0.79 V and fill factor (FF) of 68% for standard front illumination. Bifacial spectral response (SR) measurements, through front and back contacts, were analyzed and yielded a diffusion length (L) of 0.8 μm and depletion width (W) of 2.5 μm. Backwall SR measurements made through the transparent ZnTe contact are much more sensitive to L and W than are measurements for standard front illumination. ZnTe:Cu is a promising material for bifacial characterization as well as tandem cell interconnects and more stable Cu-doped contacts.