Surface passivation of Cu(In,Ga)Se2 using atomic layer deposited Al2O3

With Al2O3 passivation on the surface of Cu(In,Ga)Se-2, the integrated photoluminescence intensity can achieve two orders of magnitude enhancement due to the reduction of surface recombination velocity. The photoluminescence intensity increases with increasing Al2O3 thickness from 5 nm to 50 nm. The capacitance-voltage measurement indicates negative fixed charges in the film. Based on the first principles calculations, the deposition of Al2O3 can only reduce about 35% of interface defect density as compared to the unpassivated Cu(In,Ga)Se-2. Therefore, the passivation effect is mainly caused by field effect where the surface carrier concentration is reduced by Coulomb repulsion. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3675849]