Photocarrier collection in a-SiC : H/c-Si heterojunction solar cells

We measured the temperature dependent current-voltage (J-V) characteristics of p a-SiC:H/n c-Si heterojunction solar cells with different doping levels in the p a-SiC:H layer. For heterojunction solar cells with an undoped a-SiC:H layer, S-shaped J-V characteristics are observed at room temperature leading to poor factors. Below room temperature, such S-shape also appears for the cells with a highly doped p a-SiC:H layer. Detailed simulation studies showed that the origin of this S-shape lies in a reduced electric field in the c-Si depletion region, which, in combination with a hole accumulation at the interface, causes an increase in recombination losses. As long as the p a-SiC:H layer in these heterojunction cells is highly doped (greater than or equal to 10(19) cm(-3)), these collection problems do not occur under standard operating conditions (i.e., room temperature and 100 mW/cm(2) illumination).