Ultrafast pump-probe reflectance spectroscopy: Why sodium makes Cu(In,Ga)Se-2 solar cells better

作者：Eid Jessica; Usman Anwar; Gereige Issam; Van Duren Jeroen; Lyssenko Vadim; Leo Karl; Mohammed Omar F^*

来源：Solar Energy Materials and Solar Cells, 2015, 140: 33-37.

DOI：10.1016/j.solmat.2015.03.029

• CIGS solar cells
• Ultrafast photophysics
• Pump-probe reflectance spectroscopy
• Carrier recombination
• Dielectric function model

Although Cu(In,Ga)Se-2 (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.

• 出版日期2015-9