All-in-situ fabrication and characterization of silicon nanowires on TCO/glass substrates for photovoltaic application

Silicon nanowires (SiNWs) provide new opportunities for developing a new generation of thin film Si solar cells with enhanced light trapping and increased overall performance. Here, we report on the fabrication of SiNW-based thin film solar cells directly on top of low cost TCO/glass substrates in an all-in-situ process. The SiNWs are obtained on ITO (or SnO₂) substrates via vaporliquidsolid growth mechanism, with the nano-scaled In (or Sn) catalyst droplets prepared by using H₂ plasma superficial reduction of ITO (or SnO₂) in a plasma enhanced chemical vapor deposition system (PECVD). We demonstrate that the morphology and compositional properties of the SiNWs, as well as the catalyst remnant in the SiNWs, can be effectively controlled by tuning the growth temperature and plasma conditions. The enhanced light trapping and absorption effects have been achieved by growing SiNWs directly on top of the TCO substrates, with the absorption edge downshifting steadily to ∼1.1 eV, indicating that the crystalline core of the SiNWs also participates in the light absorption. According to a real time monitoring using an in-situ MM-16 ellipsometer, the enhanced light trapping/absorbing effects can be attributed to the growth of long, sharp and straight SiNW. Prototype SiNWs-based thin film solar cells are successfully demonstrated.