Defects passivation and crystal growth promotion by solution-processed K doping strategy toward 16.02% efficiency Cu(In,Ga)(S,Se)2 solar cells

Unsatisfactory crystal quality and deep-level defects are detrimental for Cu(In,Ga)(S,Se)(2) (CIGSSe) solar cells. In this work, an in-suit K doping strategy is implemented by introducing KF into the CIGSSe precursor solution to promote crystallization and passivate the deep defects. The effects of K on the solution-processed CIGSSe devices are systematic investigated. It has been discovered that K incorporation results in better crystallization, modified CIGSSe surface and fewer detrimental defects. Benefit from the reduction of the band-tailing effects, suppressed defects density and passivated interface recombination, the solution-processed CIGSSe solar cell achieve systematic improvement in open-circuit voltage and fill factor, enabling a champion efficiency of 16.02%, which is the highest value for alkali metal doped CIGSSe solar cells fabricated by solution-processed method. The effective in-suit K doping tactic opens an avenue for developing highly efficient solution-processed CIGSSe solar cells.