Laser-assisted Nano-texturing for Flexible Ultrathin Crystalline Si Solar Cells

This is the authors' abstract. We don't add key points for this paper.

Ultrathin crystalline Si wafers, which are more flexible than conventional ones, can apply to curved surfaces, enabling a wide range of applications such as building integrated photovoltaics, vehicle integrated photovoltaics and wearable devices. Thinner wafers require more effective light trapping; thus, surface texturing in microscale is a common approach to compensate for the reduced thickness by enhancing the light pathlength. Microscale textures, however, deteriorate the mechanical flexibility due to stress concentration in the valley of the micro-textures. In this study, we propose a laser-assisted nano-texturing process for enhanced flexibility of the ultrathin Si solar cells with a 50-µm thickness while maintaining light trapping performances. A nano-lens array was used to focus laser onto the Si wafers, inducing the formation of nanoparticle etch masks for nano-pyramid texturing in an alkaline solution. The origin of the enhanced flexibility of the nano-textured Si wafers was discussed by a micro-mechanics simulation study. We applied our nano-texturing technique to ultrathin Si based PERC cells and demonstrated the enhanced flexibility of the cells with a 26 mm critical bending radius. Also, we show that the nano-texture Si wafer provide a higher efficiency of 18.68%, whereas the micro-texture one exhibits 18.10%.