Improved Performance of Silicon Nanowire-Based Solar Cells with Diallyl Disulfide Passivation

Silicon nanowires (SiNWs) have attracted increasing attention for their enhanced light harvesting and large junction area of photovoltaic devices compared to planar silicon wafers. However, high surface recombination velocity deteriorates the photovoltaic performance of the SiNW-based solar cells. Therefore, a passivation step is necessary to avoid this effect. Here, a small organic molecule, diallyl disulfide (DADS), has been employed to passivate the surface of SiNWs. This passivation process was carried out under UV illumination at room temperature. Covalent Si-C bonds were formed between DADS and the Si surface, which was experimentally proven to reduce the surface recombination of photogenerated carriers. Compared with cells employing oxide- or hydrogen-passivated SiNWs, the power conversion efficiency of devices employing DADS-passivated SiNWs was 7.2%, which was improved by a factor of 3.8 and 1.6, respectively. Moreover, the solar cell using DADS-passivated SiNWs exhibited good stability in air. The S-shaped current-voltage curves were not observed because of the high oxidation resistance of the DADS-modified surface. This simple and effective UV-initiated passivation procedure with DADS can lower the cost and improve the photovoltaic performance of SiNW-based solar cells.