High Performance and Low Cost Passivating, Carrier-Selective Contacts for Silicon Photovoltaics

The world is now focusing on expanding renewable energy sources to reduce the carbon footprint and mitigate climate change. Solar energy is one of the most environment-friendly and fastest-growing renewable energy sources in the present world. While crystalline silicon (c-Si) based devices dominate the global photovoltaics (PV) market with a current share of 95%, it is still challenging to achieve the theoretical efficiency limit of 29.4% with this technology due to a few performance limiting factors. Contact recombination losses are dominant among them which result from the recombination of photo-generated charge carriers due to the presence of defects at the metal-semiconductor interface. These losses can be alleviated by inserting thin layers of passivating carrier selective contact (CSC) between c-Si and the overlying metal layer. Over the years different excellent passivating CSC have been developed for c-Si solar cells. In this work, new technologies are explored to improve the performance and reduce the manufacturing costs of the passivating CSC. A very promising passivating CSC for the next generation c-Si solar cell is tunnel oxide passivated doped polycrystalline silicon (poly-Si) contact. In this work, silicon oxide (SiOx) passivated phosphorus-doped poly-Si electron selective contact is developed using an in-line atmospheric pressure chemical vapor deposition process (APCVD) which is simple, low-cost, high-throughput, and well-suited for high-volume manufacturing. Another excellent passivating CSC is hydrogenated doped amorphous silicon (a-Si:H) contact which is widely used to fabricate c-Si heterojunction (SHJ) solar cells. However, this contact degrades if it is annealed at a high temperature ( \u3e \u3e 200°C) during metallization. In this work, a novel laser-sintered metal contact printing process is developed which is able to print metal fingers with low bulk resistivity without damaging the a-Si:H contact and excludes the requirement of post-metallization annealing. Along with the fabrication of these passivating CSC different optical, electrical, and materials characterization have been performed to investigate the properties and the performance of the contacts