Air-annealing of Cu(In, Ga)Se2/CdS and performances of CIGS solar cells

In this study, the annealing treatment on Cu(In, Ga)Se-2 (CIGS)/CdS interface in air is systematically investigated under different annealing temperatures from room temperature to 150 degrees C and different durations. It is found that when CIGS/CdS interface is annealed for a proper duration the corresponding CIGS thin film solar cells show enhanced open circuit voltage (V-oc) and fill factor (FF) as well as corresponding conversion efficiency. The capacitance-voltage (C-V) and time-resolved photoluminescence (TR-PL) measurement results indicate that the CIGS thin film solar cells exhibit an increase in net defect density (N-cv) and long lifetime for the carriers, respectively, after the annealing treatment of CIGS/CdS at a mediate annealing temperature here. Moreover, the net defect density of annealed solar cells at higher annealing temperatures for a long duration is reduced. All the variations in the solar cell performances, N-Cv and carrier lifetime would be related to the passivation of Se vacancies and In-Cu defects, surface (interface) states as well as positive interface discharges and Cu migration etc. A high efficiency CIGS solar cell o f 14.4% is achieved. The optimized solar cell of 17.2% with a MgF2 anti-reflective layer has been obtained. (C) 2017 Elsevier B.V. All rights reserved.