High-Efficiency Amorphous Silicon Solar Cells with ZnO as Front Contact

Abstract

B-doped ZnO films deposited by the photo-induced metalorganic chemical vapor deposition (photo-MOCVD) method were applied to p-i-n single junction amorphous silicon (a-Si) solar cells as front contacts. The thickness and the doping level of the p-layer were optimized in order to increase the open-circuit voltage (V _oc) of the fabricated a-Si solar cells. As a result, a stabilized conversion efficiency of 8.7% (V _oc: 0.926 V, J _sc: 14.6 mA/cm², FF: 0.646) was achieved under AM 1.5 (100 mW/cm²) illumination. Furthermore, the electrical properties of ZnO films were improved by employing an atomic layer deposition (ALD) technique instead of the conventional MOCVD method, and a lower resistivity of 5×10^-4 Ωcm was achieved. It was also found that the stability of the electrical properties of ZnO films was improved by the ALD technique. The performance of the a-Si solar cells was further improved by applying the obtained high-quality ZnO films.