Photoluminescence Characterization and Passivation of CIGS Absorber

The photoluminescence is used to monitor the optical property of the Cu(In,Ga)Se2 solar cell. The temperature dependent external quantum efficiency shows the influence of defects in optical response and the band gap shift of Cu(In,Ga)Se2 at elevated temperature. The emission peaks at 1.03 and 1.1 eV are due to electrons in conduction band edge and donor state to recombine with holes in acceptor state, respectively. Competitiveness of these two transition mechanisms is studied with different pumping power and varied temperature by photoluminescence. The defect level and relative defect density can be obtained by the transition models. The Al2O3 is used to passivate the surface of CIGS absorber and enhance the photoluminescence intensity.