All-sputtered CdTe solar cell activated with a novel method

Abstract

CdTe thin film solar cells are usually fabricated depositing the absorber layer by Close Space Sublimation (CSS) and Vapor Transport Deposition (VTD), mainly due to the high deposition rate allowed by these techniques. However, most of the solar cell films can be deposited by sputtering, making to deposit also the CdTe by this technique attractive. Indeed, an all-sputtered solar cell could be deposited in one sequential chamber at a relatively low temperature and without breaking the vacuum, resulting in a sensible decrease in the production cost at the industrial level. Usually, treatments based on CdCl2, also known as activations, are applied to the CdTe solar cells to achieve high power conversion efficiency (PCE). However, it was observed that the usual activation methods could be aggressive for all-sputtered CdTe solar cells, damaging the films and resulting in low performance. In this work, we propose a novel activation method based on Nitrogen/Oxygen/CHCIF2 gas mixture, which is more suitable for this kind of device. Morphological, structural, optical and electrical properties were analyzed and compared to our CSS-CdCl2 baseline. A PCE of 12% was achieved for all-sputtered CdTe solar cells.