A structural study on the CuGaSe₂‐related copper‐poor materials CuGa₃Se₅ and CuGa₅Se₈: thin‐film vs. bulk material

Abstract

Polycrystalline samples of CuGaSe2‐related defect compounds (DC) have been prepared by Chemical Close‐Spaced Vapour Transport (CCSVT) (thin films) and elemental synthesis (powder) respectively. In the latter case a homogenisation step was introduced during the preparation, including mechanical intermixing and adjacent‐heat treatment after the main reaction. Following this route we assured conditions “close to” thermodynamic equilibrium. The influence of the annealing temperature on the lattice parameters a0 and c0, as well as the cation distribution, was investigated. By means of X‐ray and neutron diffraction analysis the structural properties of the Cu–Ga–Se based DCs have been determined and a new structural model has been derived. Finally the structural parameters of CCSVT‐grown thin‐film material were correlated with findings for bulk material samples which were intentionally prepared off‐equilibrium. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Long-range structure of Cu(InxGa1−x)3Se5: A complementary neutron and anomalous x-ray diffraction study

“…For detailed information about sample preparation and the impact of the annealing and annealing temperature on the compositional and structural properties of the samples see Ref. 13.…”

“…We conclude that probably most of the enumerated material properties of a given compound can be attributed to the issue of the synthesis regime, a conclusion we have recently reported about for pure CuGa 3 Se 5 and CuIn 3 Se 5 -CuGa 3 Se 5 alloy samples. 13,14 …”

“…This part will not be discussed in detail here, as the relevant information can be found elsewhere. 13,14 Second, the structural parameters of the samples as a function of their composition were extracted from full-pattern analysis of neutron powder diffraction experiments, while the occupation factors were obtained from a combination of neutron and anomalous x-ray diffraction ͑XRD͒ methods. One aspect is of special importance for a conclusive structural characterization of these compounds, namely, the distinction of scattering contributions of the isoelectronic species Cu + and Ga 3+ , which is, by itself, a challenging task and almost impossible to solve with standard x-ray and electron diffraction techniques.…”

Structural investigation of the Cu2Se–In2Se3–Ga2Se3 phase diagram, X-ray photoemission and optical properties of the Cu1−z(In0.5Ga0.5)1+z/3Se2 compounds

“…These so-called ordered vacancy compounds (OVC) have been investigated as bulk materials by powder diffraction [9][10][11][12] and it was noticed that the corresponding structures remain tetragonal with c E2a.…”

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

“…Also, the passivation of the back interface with point contact formation may be an effective approach to reduce interface recombination . Another possible approach to modify the energy band diagram in CGSe films and the p‐n junction interface formation in CGS devices is the control and use of Cu‐deficient phases such as CuGa 3 Se 5 and CuGa 5 Se 8 . For example, CuIn 3 Se 5 and CuGa 3 Se 5 have been known to have E g values of 1.20 and 1.85 eV, respectively .…”