Improvement of silicon solar cell efficiency by ion beam sputtered deposition of AlO_xN_y thin films

Negative charge material, AlOxNy, has been fabricated to passivate the surface of p-type silicon. The fabrication of AlO_xN_y was possible by using ion beam sputtering deposition to deposit AlN thin film on the surface of a p-type silicon wafer and following annealing in oxygen ambient. Capacitance-voltage analysis shows the fixed charge density has increased from 1011 cm^-2 to 2.26 × 1012 cm^-2 after annealing. The solar cell efficiency increased from 15.9% to 17.3%, which is also equivalent to the reduction of surface recombination velocity from 1 × 10⁵ to 32 cm/s.