Plasma etching: a strategy to enhance the photovoltaic conversion efficiency of ultrathin CdTe solar cells

Ultrathin CdTe solar cell is a promising application of using integrated photovoltaics to act as architectural components and bifacial devices to promote the utilization of sunlight. In the preparation process of the ultrathin CdTe solar cells, the chemical solution etching process before back contact deposition has to be refrained due to the high risk of shunting. Therefore, an alternative strategy to get a clean CdTe surface is required. In this work, plasma etching treatment was conducted on sputtered ultrathin CdTe films to eliminate the residual oxides induced by CdCl2 treatment. Furthermore, ultrathin bifacial CdTe solar cells with a structure of glass/FTO/SnO2/CdS/CdTe (∼920 nm)/CuCl/ITO were fabricated to investigate the effect of plasma etching on the device performance. As a result, by employing plasma etching treatment, a bifacial device with a front illuminated efficiency of up to 9.93% and a rear illuminated efficiency of 2.41% was achieved. This work provides important indications for the performance optimization of ultrathin CdTe solar cells.