The present work prepared the CuIn 3Se 5 ingots by using a horizontal Bridgman method and investigated the Energy Dispersive Spectrometry (EDS) and X-Ray Diffraction (XRD) to calculate the compositions of the ingots. Photoluminescence was used to check their optical properties. It was found that CuIn 3Se 5 had either a Stanite structure, an Ordered Defect Chalcopyrite (ODC) structure, or an Ordered Vacancy Chalcopyrite (OVC) structure. The gap energy obtained by Photoluminescence (PL) for the different samples is 1.23 eV. Studying the variation of the gap as a function of the temperature shows that the transition is a D-A type.
Cu(In,Ga)Se2 is one of the most promising semiconductors for the absorber-layer of thin-film solar cells [
Crystals with different compositions were synthesized by direct combination of high purity 5N for Cu and In, 6N for Ga and Se in the desired proportions. The elements were placed in a quartz tube sealed under a vacuum of 5 × 10−6 Torr. This tube was placed ina horizontal heater that reached a temperature exceeding the melting point of the compound. It was left in the heater for 72 hours at which point it was allowed to slowly cool down [
To characterize the crystals, X-Ray Diffraction was carried out using a Seifert MZIV powder diffractometer (q, 2q geometry) with Cu (Ka) radiation (l = 1.5406 Ǻ). The chemical composition of the obtained samples were given by EDS (Link type AN 1000 55/S) coupled to a scanning microscope (Cambridge type S360). The Photoluminescence (PL) measurements were performed at different temperatures (from 4.2 K to 85 K) by directly immersing the samples into liquid helium. Excitation was provided by a 632.8 nm He-He laser (20 mW). The illumination of the samples was realized using fiber optic light guides (UV-visible). A3 mm spot was focused on the sample with a power of 2 mW/cm2. The emission spectrum, collected through another fiber (visible-IR), was analyzed using a grating monochromator (30 cm focal length, 600 lines/mm, blazed at 760 nm).
In
The spectra of different CuIn3Se5 samples obtained by X-Ray Diffraction are shown in
Sample (E) was studied using X-Ray Diffraction (
CuIn3Se5 | |||||
---|---|---|---|---|---|
samples | % Cu | % In | % Se | Dy | conductivity type |
A | 11.2 | 32.4 | 56.4 | +0.037 | n |
B | 11.3 | 32.9 | 55.8 | +0.030 | n |
C | 11.2 | 32.5 | 56.3 | +0.034 | n |
D | 11.3 | 33 | 55.7 | +0.027 | n |
E | 14.8 | 31.5 | 53.3 | +0.409 | n |
Peaks located at 2θ = 11.4˚, 21.21˚, 13.04˚ and 30.96˚ indicated by the symbol (*), represent the InSe phase.
Peaks located at 2θ = 15.28˚ and 26˚ indicated by the symbol (?) can be associated with a CuIn2Se3.5 phase [
The presence of these phases in the case of CuIn3Se5 is sometimes possible when CuIn3Se5 is equivalent to the CuInSe2 compound with indium excess. The a and c lattice parameters of CuIn3Se5 presented in
CuIn3Se5 | a | c | c/a | Δ(c/a) |
---|---|---|---|---|
A | 5.76 | 11.52 | 2.0015 | +0.0015 |
B | 5.72 | 11.43 | 1.9995 | −0.0005 |
C | 5.65 | 11.295 | 1.999 | −0.0010 |
D | 5.62 | 11.262 | 2.0032 | +0.0032 |
E | 5.59 | 11.28 | 2.016 | +0.0160 |
found by varying the temperature of the CuIn3Se5 samples. In the case of CuIn3Se5, the fiber optic presents absorption at 1 eV, because of this the corrected photoluminescence spectrum of the fiber absorption shows two peaks.
The full width at half maximum (FWHM) of the peak is found to be in the order of 105 meV. This value shows that the transition is a D− A type. Since CuIn3Se5 is equivalent to CuInSe2 with an indium excess, the defects that appear are probably InCu, VCu and InSe. Defect InCu is more probable than VCu and InSe given that it has a low formation energy ε [
Eg = 1.23 − 0.0008 T
In order to distinguish a D-A transition from other types of transitions, a method of increasing the excitation power and observing a shift of the peak toward high energies was used (
transition. In a D-A type transition, it is known [
The variation of the light intensity of CuIn3Se5 emission peak as a function of the excitation power at a constant temperature of 4.2 K is shown in
Firstly, samples of CuIn3Se5 have been prepared by the Bridgman method. The different samples have then been characterized by several techniques (EDS, XR, hot point probe and photoluminescence). All but one sample present good stœchiometry and are well crystallized. Their lattice parameters a and c are similar to those in previous publications, specifically c/a » 2. The characterization by photoluminescence allowed the gap value of 1.23 eV to be determined for these compounds. Studying the variation of the gap as a function of the temperature showed that the variation coefficients of the gap along with the temperature of our CuIn3Se5 compounds had the same order of magnitude. These coefficients were found to be negative for our samples. The CuIn3Se5 sample differed from the rest as it was from good stœchiometry. Further analysis of this sample showed the existence of other secondary phases (InSe and CuIn2Se3.5).
The authors wish to express their sincere thanks to Marcelle Farhat for her helpful collaboration.
Dayane Habib,Ouloum Aoudé,Slyman Karishy,Georges El Haj Moussa, (2015) Fabrication, Characterization and Optical Properties of CuIn3Se5 Bulk Compounds. World Journal of Condensed Matter Physics,05,201-208. doi: 10.4236/wjcmp.2015.53021