Reversible correlation between subnanoscale structure and Cu content in co-evaporated Cu(In,Ga)Se2 thin films

Short-range versus long-range structure in Cu(In,Ga)Se2, Cu(In,Ga)3Se5, and Cu(In,Ga)5Se8

“…Element-specific bond lengths and bond length variations were determined by extended X-ray absorption fine structure spectroscopy (EXAFS). Comparison with our previous studies of Cu(In,Ga)Se 2 [30,33,34] provides a systematic investigation of the effects of both composition and stoichiometry on these local structural parameters. A significant difference between the crystallographic long-range structure and the element-specific short-range structure becomes evident, contributing to a…”

Heavy Alkali Treatment of Cu(In,Ga)Se2Solar Cells: Surface versus Bulk Effects

“…Tail states can be caused by any imperfection of the crystal. In polycrystalline Cu(In,Ga)Se 2 absorbers they can be caused by electrostatic potential fluctuations, by bond length variations, by composition variations that change the bandgap, and by effects of grain boundaries . To study the effect of different alkali‐fluoride PDTs on the electrostatic band bending at grain boundaries, Kelvin probe force microscopy (KPFM) experiments were performed on a set of three samples where the Cu(In,Ga)Se 2 absorber was grown by an identical high‐temperature process (which was optimized for RbF‐PDT) and subsequently a KF‐, RbF‐, or CsF‐PDT was applied .…”

How band tail recombination influences the open‐circuit voltage of solar cells

“…According to Cody et al 1 and John et al 44 , Urbach tails are caused by phonons and by static disorder, that is, by lattice vibrations and defects, that lead to deviations from the perfect crystal lattice. In the case of CIGSe, origins of disorder and hence Urbach tails are likely to be related to variations in the bond lengths 45 and potential fluctuations of which there are two kinds: band gap fluctuations and electrostatic potential fluctuations 2,46 …”