Pulsed laser annealing of spray casted Cu(In,Ga)Se2 nanocrystal thin films for solar cell application

We report ambient processing of 2.5 mu m thick layers of Cu(In,Ga)Se-2 (CIGS) nanocrystals thin films sprayed on CdS/i:ZnO/Al:ZnO/Soda lime glass substrates with pulsed laser annealing (PLA), using 1064 nm laser at 220 ns pulse width for solar cell fabrication. The choice of the nanosecond pulse width of the near-infrared laser source is critical for the effectiveness of the laser sintering of the CIGS layer irrespective of substrate thermal stability. Solid state sintering by PLA post treatment is evidenced via morphological and structural analysis. The analysis confirms the improvement in the quality of CIGS absorber with respect to its grain size from 5 nm to 20 nm after PLA, which is expected to reduce deep level defects. The short circuit current density of photovoltaic devices prepared using ambient processed laser annealed absorber layer increased significantly from 0.75 mA cm(-2) to 8 mA cm(-2), resulting in reasonable power conversion efficiency exceeding 1%. The promising results realized by PLA treatment, presented in this work, have great potential to be integrated into scalable roll-to-roll manufacturing of CIGS solar cells.