The influence of post-deposition annealing upon amorphous silicon/crystalline silicon heterojunction solar cells

• We studied the impact of the thermal annealing on the silicon heterojunction solar cells.
• Compared were samples deposited by ICP-CVD and PE-CVD methods.
• Annealing up to 250 °C improves output performance of both solar cells.
• Annealing above 250 °C increases defect states density at the interface and in the amorphous emitter.
• Samples deposited by ICP-CVD shows better resistance against annealing.

This paper presents a comparative study of the influence of post-deposition annealing on amorphous silicon/crystalline silicon heterojunction solar cells deposited by ICP-CVD and PE-CVD techniques. Two major effects on the solar cell efficiency occur caused by thermal annealing. The first effect is a slight improvement of the performance on annealing up to 250 °C. The second effect, for annealing temperatures above 250 °C, reveals deterioration of the solar cell performance. It is suggested that both effects are related to thermally activated diffusion of hydrogen. For low annealing temperatures, diffusion of weakly bonded hydrogen allows to passivate the defects in the amorphous emitter and at the heterointerface. In the high temperature annealing region, outdiffusion of hydrogen is assumed to be responsible for an increase of defect states in the structures. The results indicate a better stability after high temperature treatment for the sample prepared by ICP-CVD technology.