Development of High-Quality P-Type Si Thin-Films by a New SPC Method and its Application to Solar Cells

Abstract

In order to establish low-cost solar cell technology using crystalline silicon, it is necessary to develop a low temperature p-n junction fabrication process by which large-area solar cells can be produced. We have tried to prepare the p-n junction by depositing high-quality p-type Si. Highly conductive p-type Si thin-films were prepared at the low temperature of 650°C, using the new solid phase crystallization (SPC) method. In this SPC method, amorphous silicon (a-Si) films deposited by plasma-CVD were used as a starting material. These films have a conductivity of more than 1×103 (Ωcm)−1 on the quartz substrate, which is the highest ever reported on p-type Si prepared by a low-temperature process. Concerning the surface morphology of substrate, it was found that the mobility of p-type Si on the textured substrate was 3∼7 times higher than that of p-type Si on the flat substrate, where maximum value was 32.2cm2/Vs at the carrier concentration of 2×1020 cm−3. These films were applied to p-layers in solar cells using textured single crystalline silicon (c-Si). Using 2cm2 sized p-n junction solar cells prepared by the SPC method, a high conversion efficiency of 14.2% has been achieved. Therefore, p-type Si thin-films prepared by the SPC method are of high-quality, and it is considered that the SPC method has high potential from the viewpoint of low-cost solar cell fabrication.