PHOTOCARRIER COLLECTION IN A-SIC-H C-SI HETEROJUNCTION SOLAR-CELLS/

We measured the temperature dependent current-voltage (J-V) characteri stics of p a-SiC:H/n c-Si heterojunction solar cells with different do ping levels in the p a-SiC:H layer. For heterojunction solar cells wit h an undoped a-SiC:H layer, S-shaped J-V characteristics are observed at room temperature leading to poor factors. Below room temperature, s uch S-shape also appears for the cells with a highly doped p a-SiC:H l ayer. Detailed simulation studies showed that the origin of this S-sha pe lies in a reduced electric field in the c-Si depletion region, whic h, 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 t hese heterojunction cells is highly doped (greater than or equal to 10 (19) cm(-3)), these collection problems do not occur under standard op erating conditions (i.e., room temperature and 100 mW/cm(2) illuminati on). (C) 1998 Elsevier Science B.V. All rights reserved.