Hydrogenated Amorphous Silicon Oxide (A-Siox:H) Single Junction Solar Cell With 8.8% Initial Efficiency By Reducing Parasitic Absorptions

Hydrogenated amorphous silicon oxide (a-SiOx:H) solar cells have been successfully implemented to multi-junction thin film silicon solar cells. The efficiency of these solar cells, however, has still been below that of state-of-the-art solar cells mainly due to the low J(sc) of the a-SiOx: H solar cells and the unbalanced current matching between sub-cells. In this study, we carry out optical simulations to find the main optical losses for the a-SiOx: H solar cell, which so far was mainly optimized for V-oc and fill-factor (FF). It is observed that a large portion of the incident light is absorbed parasitically by the p-a-SiOx: H and n-a-SiOx:H layers, although the use of these layers leads to the highest V-oc X FF product. When a more transparent and conductive p-nc-SiOx:H layer is substituted for the p-a-SiOx:H layer, the parasitic absorption loss at short wavelengths is notably reduced, leading to higher J(sc). However, this gain in J(sc) by the use of the p-nc-SiOx:H compromises the V-oc. When replacing the n-a-SiOx:H layer for an n-nc-SiOx:H layer that has low n and k values, the plasmonic absorption loss at the n-nc-SiOx:H/Ag interfaces and the parasitic absorption in the n-nc-SiOx:H are substantially reduced. Implementation of this n-nc-SiOx:H leads to an increase of the J(sc) without a drop of the V-oc and FF. When implementing a thinner p-a-SiOx:H layer, a thicker i-a-SiOx:H layer, and an n-nc-SiOx:H layer, a-SiOx:H solar cells with not only high J(sc) but also high V-oc and FF can be fabricated. As a result, an 8.8% a-SiOx:H single junction solar cell is successfully fabricated with a V-oc of 1.02 V, a FF of 0.70, and a J(sc) of 12.3 mA/cm(2), which is the highest efficiency ever reported for this type of solar cell.