Ultrafast pump-probe reflectance spectroscopy: Why sodium makes Cu(In,Ga)Se2 solar cells better

Ultrafast pump-probe reflectance spectroscopy: Why sodium makes Cu(In,Ga)Se2 solar cells better

Ultrafast pump-probe reflectance spectroscopy: Why sodium makes Cu(In,Ga)Se2 solar cells better
Jessica Eid, Anwar Usman, Issam Gereige, Jeroen Van Duren, Vadim Lyssenko, Karl Leo, Omar F. Mohammed
Solar Energy Materials and Solar Cells, 140, pp 33–37, (2015)
Jessica Eid, Anwar Usman, Issam Gereige, Jeroen Van Duren, Vadim Lyssenko, Karl Leo, Omar F. Mohammed
CIGS solar cells, Ultrafast photophysics, Pump-probe reflectance spectroscopy, Carrier recombination, Dielectric function model
2015
Although Cu(In,Ga)Se2 (CIGS) solar cells have the highest efficiency of any thin-film solar cell, especially when sodium is incorporated, the fundamental device properties of ultrafast carrier transport and recombination in such cells remain not fully understood. Here, we explore the dynamics of charge carriers in CIGS absorber layers with varying concentrations of Na by femtosecond (fs) broadband pump-probe reflectance spectroscopy with 120 fs time resolution. By analyzing the time-resolved transient spectra in a different time domain, we show that a small amount of Na integrated by NaF deposition on top of sputtered Cu(In,Ga) prior to selenization forms CIGS, which induces slower recombination of the excited carriers. Here, we provide direct evidence for the elongation of carrier lifetimes by incorporating Na into CIGS.





DOI:10.1016/j.solmat.2015.03.029