Kavli Affiliate: Peidong Yang
| First 5 Authors: Hugo Laurell, Jonah R. Adelman, Elizaveta Yakovleva, Carl Hägglund, Kostiantyn Sopiha
| Summary:
In this study, coherent phonon motion is observed in bandgap excited
CuIn$_{x}$Ga$_{(1-x)}$Se$_2$ (CIGS) utilizing extreme ultraviolet (XUV)
attosecond transient absorption spectroscopy across the Se M$_{4,5}$ absorption
edge. Two frequencies of coherent phonon motion are resolved, a low frequency
mode attributed through Raman measurements to the $A_{1g}$ phonon motion of a
Cu-deficient ordered vacancy compound (OVC), while the high frequency mode
originates from the $A_{1g}$ phonon motion in the chalcopyrite phase. The two
oscillations lead to modulations in the XUV differential absorption $Delta
A(epsilon,tau)$ due to energy shifts of the Se M$_{4,5}$ edge, with a minima
occuring approximately 1 ps after the band gap excitation. The hot carrier
cooling time of holes and electrons are disentangled and the observed slower
cooling of holes is attributed to the higher density of hole states in the
valence band. We also observe fast oscillations (18.6(3) fs period) across the
Se absorption edge, which are interpreted to originate from quantum path
interference between the electronic conduction bands of the chalcopyrite CIGS
and OVC phases, opening the possibility towards quantum coherent metrology in
photovoltaics on the femtosecond timescale. The complex interplay between the
chalcopyrite and OVC phases are revealed in this investigation through both
coherent vibrational and electronic motions.
| Search Query: ArXiv Query: search_query=au:”Peidong Yang”&id_list=&start=0&max_results=3