Amorphous silicon/p-type crystalline silicon heterojunction solar cells with a microcrystalline silicon buffer layer

Undoped hydrogenated amorphous silicon (a-Si:H)/p-type crystalline silicon (c-Si) structures with and without a microcrystalline silicon (mu c-Si) buf fer layer have been investigated as a potential low-cost heterojunction (HJ ) solar cell. Unlike the conventional HJ silicon solar cell with a highly d oped window layer, the undoped a-Si:H emitter was photovoltaically active, and a thicker emitter layer was proven to be advantageous for more light ab sorption, as long as the carriers generated in the layer are effectively co llected at the junction. In addition, without using heavy doping and transp arent front contacts, the solar cell exhibited a fill factor comparable to the conventional HJ silicon solar cell. The optimized configuration consist ed of an undoped a-Si:H emitter layer (700 Angstrom), providing an excellen t light absorption and defect passivation, and a thin mu c-Si buffer layer (200 Angstrom), providing an improved carrier collection by lowering barrie r height at the interface, resulting in a maximum conversion efficiency of 10% without an anti-reflective coating. (C) 2000 Elsevier Science B.V. All rights reserved.