Photoluminescence study of the defect-induced recombination in Cu(In,Ga)Se2 solar cell

• We study the effects of RTA treatments on both the defects and the carrier recombination of CIGS solar cells.
• We provide an optimized post annealing condition.
• Suitable annealing temperature can reduce the deep level defects InCu of CIGS layer.
• Suitable annealing temperature can effectively reduce the recombination and improve the performance of CIGS device.
• Higher annealing temperature eventually leads to the device performance decay due to the increase of the interface state.

In this paper, a series of recombination paths in Al:ZnO/ZnO/CdS/Cu(In,Ga)Se2 (CIGS) solar cell has been carried out through photoluminescence (PL) emission, optoelectronic conversion characteristic and AFORS HET simulation. Proper rapid thermal annealing (RTA) lead to the improvement of CIGS performance by reducing bulk recombination of CIGS layer and interface recombination, which opens the way to explore a useful method to significantly ameliorate the microstructure within the CIGS layer. A maximum value for the conversion efficiency was obtained when the annealing temperature was continuously increased to 400 °C, where the efficiency increased by 43%, and the recombination from the interface states, the bulk defect traps and the tunneling enhancement recombination was reduced to the lowest. The opto-electronic parameters, such as short-circuit current Jsc, open-circuit voltage Voc, reverse saturation current J0 and the series resistance Rs have been correlatively investigated to the nonradiative transition among the various defects and are strongly dependent upon the annealing temperature as well.