Enhanced recombination next to laser-patterned lines in CIGSe solar cells revealed by spectral and time-resolved photoluminescence

摘要

Laser-based patterning of CIGSe solar cell absorber layers for monolithic series connection by nanosecond (ns) and picosecond (ps) laser pulses introduces material modifications in the vicinity of the patterned lines, which affect the CIGSe composition, the electrical properties, the extent of the dead area and finally the efficiency of the complete solar cell. Here, spectral and time-resolved photoluminescence is used to show that Cu vacancies and anti-sites are formed next to the edges of the scribe lines, which lead to the formation of additional energy states in the band gap near the valence band edge. A significant reduction in charge carrier lifetime is noted as the scribed lines are approached from unaffected areas of the material. Since this effect is absent in the mechanical needle patterning, it can clearly be attributed to the influence of the laser pulses. Despite the laserinduced material modification, laser-based CIGSe patterning outperforms needle-based patterning. Advantages regarding the width of the affected edge areas were observed when using ns pulses instead of ps pulses, which could be due to the lower peak intensities.