Formation of PN junctions for crystalline silicon solar cells by means of infrared laser irradiation

We report on our approach for developing a potentially low-cost process for fabricating a p-n junction for a crystalline Si solar cell using a cheaper infrared laser. The proposed process was that dopants film and a carbon infrared absorption film were sequentially formed by spin-coating method on a Si wafer and then it was irradiated with the infrared laser. The process was applied to phosphorus doping in p-type single and multi-crystalline wafers. A low sheet resistance of less than 100 Ω/ was obtained for the phosphorus(P)-doped layers of both Si wafers. In addition, a p-n junction depth of 100 nm was achieved for the single crystalline wafer. Good-quality diode I–V characteristics were also obtained. As another approach, a p-n junction was fabricated by crystallizing a P-doped a-Si film formed on a Si substrate with the laser. A suitable condition for the crystallization was explored and it was applied to fabricating a simplified solar cell. The fabricated sample showed I–V characteristics as a solar cell under light illumination.