Deep level emission in polycrystalline CuGaSe₂ thin-films observed by micro-photoluminescence

Abstract

Polycrystalline CuGaSe 2 thin-films with various Cu-contents were deposited by three-stage co-evaporation method. Radiative transitions in the CuGaSe 2 were studied by micro-photoluminescence technique in relation to the Cu/Ga ratio in the films. In addition to a peak DAP1 around 1.60 eV, a peak DAP2 at relatively lower energy of 1.35 eV and a broadened deep-level emission DL roughly centered at 1.05 eV were observed in the photoluminescence (PL) spectra of the CuGaSe 2 films. Excitation-power dependence along with temperature dependence of the PL suggests that dominant recombination mechanism due to donor-acceptor pair recombination at lower temperature becomes impurity-to-band transition at higher temperature for all the three peaks. A deep donor-level, roughly 630 meV below the conduction band, which corresponds to DL-emission has been confirmed, and was investigated further in relation to the compositional variation in the CuGaSe 2 films.

First-principles study of defects at $\Sigma3$ grain boundaries in CuGaSe$_2$

“…Other research groups focus on the electronic properties of the materials involved and on how they are affected by defects and impurities. In this regard, important attention has been given to defects in bulk CuGaSe 2 [5,10,18,19,20,21] and at grain boundaries in CuGaSe 2 [5,18,22,23].…”

CuGaSe2 Thin Film Solar Cells: Challenges for Developing Highly Efficient Wide‐Gap Chalcopyrite Photovoltaics

“…On the other hand, there is room for further improvement in wide‐gap (1.5 eV or larger) chalcopyrite solar cells before practical applications can be considered. In contrast to narrow‐gap CIGSe‐based solar cells, the amount of effort dedicated to developments in wide‐gap chalcopyrite solar cells has been limited, though there have been a relatively large number of fundamental studies undertaken including comparative studies on the material properties of CGSe, CISe, and CIGSe . These fundamental studies include, for example, epitaxial film growth and electro‐optical property measurements, theoretical and experimental studies in terms of defects formation, and the effects of impurities, and so on.…”