In this work, AMPS-D (Analysis of Microelectronic and Photonic Structures)mode was used to simulate hetero-junction amorphous silicon solar cell. The influence of energy band mismatch at p/i interface and Schottky barrier at TCO/p or n/metal interfaces on light I-V characteristics was investigated on a solar cell with a pin structure of TCO/p-a-SiC:H/i-a-Si:H/n-a-Si:H/metal. Simulation shows that the energy band mismatch at p/i interface is the main cause of the abnormal bending of the light I-V curves in a voltage range of less than the open circuit voltage (Voc). Schottky barrier Ep at TCO/p or En at n/metal interfaces causes the light I-V curve bending in a voltage range higher than Voc.