Influence of post-deposition heat treatment on electrical transport properties of In2S3-buffered Cu(In,Ga)Se2 cells

The electrical characteristics of Cu(In,Ga)Se2-based solar cells with In2S3 buffer were investigated. The effects of post-deposition annealing in helium or in air on current–voltage characteristics, net acceptor density profiles and admittance spectra were studied. Analysis of the current–voltage characteristics showed that interface recombination dominated transport in the as-deposited devices was reduced after annealing and partially replaced by bulk recombination. This was accompanied by a decrease in the saturation current and diode ideality factor. The influence of the heat treatment on the buffer/hetero-interface region as determined by capacitance measurements was minor. We conclude that a reduction in the interface states density and in the p + layer doping caused by the chemical modification of the hetero-interface region is the major source of the improvement.

► Heat treatment reduces interface recombination in ZnO/In2S3/Cu(In,Ga)Se2 cells.
► Treatment inflicts minor changes on admittance spectra and doping profiles.
► Heat treatment reduces tunneling to interface states.