Aluminum-doped crystalline silicon and its photovoltaic application

The impact of Al doping with the concentrations in the range of 0.01-0.1 ppmw on the performance of silicon wafers and solar cells is studied. The effective segregation coefficient of impurity keff of Al in Si is obtained as 0.0029, which is calculated as 0.0027, supporting that Al should be totally ionized and occupy the substitutional sites in silicon and serve as the +1 dopant. It is found that the open-circuit voltages (Uoc), short-circuit currents (Isc) and photo-electrical conversion efficiency of the Al-containing solar cells decrease with the increase of Al concentrations because of Al-related deep level recombination centers. The average absolute efficiency of Al-doped silicon solar cells is 0.34% lower than that of Ga-doped-only cells, and the largest difference can be about 0.62%. Moreover, Al doped silicon solar cells show no light induced efficiency degradation, and the average efficiency maintains above 17.78%, which is comparable at the final state to that of normal B-doped silicon solar cells.