Investigation on the performance of Mo2N thin film as barrier layer against Fe in the flexible Cu(In,Ga)Se2 solar cells on stainless steel substrates

In the present work, flexible Cu(In,Ga)Se2 (CIGS) solar cells were prepared from annealing and post-selenization of electrodeposited Cu/In/Ga precursor layers on stainless steel (SS) substrates. The Mo2N thin film was fabricated by radio-frequency (RF) reactive magnetron sputtering deposition and was proposed as a barrier layer to restrain the diffusion of Fe into the CIGS film. It was observed that the insertion of a Mo2N barrier layer had no influence on the crystal structure nor the morphology of the Mo and CIGS films, as identified and confirmed by X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM). In addition, secondary ion mass spectrometry (SIMS) analysis indicated that the Mo2N barrier layer significantly reduced the diffusion of Fe into the CIGS film. The performance of the flexible CIGS solar cell was dramatically improved due to the reduced Fe concentration in the CIGS film. Finally, the flexible CIGS solar cell with a Mo2N barrier layer demonstrated an enhanced conversion efficiency of 6.86%, compared to that of a solar cell (3.45%) without a Mo2N barrier layer.