A new interdigitated back contact silicon solar cell with higher efficiency and lower sensitivity to the heterojunction defect states

Abstract

A new interdigitated back contact silicon heterojunction (IBC-SHJ) solar cell with two additional buffer layers is investigated. The buffer layers are two thin p-type crystalline silicon (c-Si) layers placed at front and back surface of c-Si/a-Si:H hetero-junction interfaces. Improvement of the overall efficiency and decrease in sensitivity of the output parameters to c-Si/a-Si:H interface defect density through the controlling of carrier concentration by introducing the new structure is achieved. The impact of new buffer layers on the cell performance is studied with numerical modeling. The main output parameters of the IBC-SHJ solar cell including buffer layers are compared with the conventional IBC-SHJ solar cell. It is found that the new IBC-SHJ solar cell has a higher fill factor due to reduced series resistance. With a deeper study on the impact of the buffer layers, it is realized that the field effect passivation has a key role in the improvement of the new cell performance. By modifying the energy band structure through the buffer layers, recombination at the c-Si/a-Si:H heterojunction interfaces is reduced due to the field effect passivation of the c-Si surface, and the efficiency of the solar cell is increased. Optimizing doping concentration and thickness of the buffer layers leads to an increase of 5% in fill factor and an increase of 1.2% in efficiency compared with the conventional similar solar cell.