Growth and characterization of CuIn_1−xAl_xSe₂thin films deposited by co-evaporation

Abstract

CuIn1−xAlxSe2 thin films (x = 0–1.0) were prepared by the four-source co-evaporation technique onto soda lime glass substrates held at 673 K. The films are found to be nearly stoichiometric as determined from Rutherford back scattering (RBS) analysis. Surface analysis of the films was carried out by x-ray photoelectron spectroscopy. X-ray diffraction and scanning electron microscopy are used to examine the structure of the films. The films are found to be single phase and chalcopyrite in structure. The lattice parameters are found to vary nonlinearly with x. Optical absorption studies reveal a three-fold optical band structure and the band gaps are found to increase nonlinearly with the increase in Al content. Crystal field and spin–orbit parameters are determined from the band gaps using a quasi-cubic model. The deformation potential and the percentage of d-orbital contribution to p–d hybridization are determined using the deduced crystal field and spin-orbit parameters. All the films are p-type conducting and the resistivity is found to increase with the increase in Al content. Room temperature Hall mobility and the carrier concentration of the films are determined.

CuIn1−xAlxS2 thin films prepared by sulfurization of metallic precursors

“…Their values varied also nonlinearly from {a = 5.49Å, c = 11.02Å} for CuInS 2 to {a = 5.30Å, c = 10.36Å} for CuAlS 2 . The same nonlinear behavior was observed in previous work focused on thin films of a similar chalcopyrite, CuIn 1−x Al x Se 2 [21][22][23][24]. Reddy at al.…”

Study of the Al-grading effect in the crystallisation of chalcopyrite CuIn1−xAlxSe2 thin films

“…The precursor layers and elemental selenium were put together within a partially closed graphite box which was loaded in a quartz tube furnace for selenisation at different temperatures. Selenisation took place at 1,013·10 5 Pa under an Ar flux that remains constant throughout the process. The selenisation process was carried out in three steps as described in previous works [9,10].…”

“…On the other hand, for equivalent substitution, aluminium produces a larger band gap change in CIS than Ga due to the smaller size of the Al atom [3]. Thus, the CuIn 1-x Al x Se 2 (CIAS) compound allows the adjustment of the energy band gap from Eg=1.0 eV (CuInSe 2 ) to Eg= 2.7 eV (CuAlSe 2 ) [4], allowing its use in single and multi-junction solar cells [5]. The optimum band gap for terrestrial applications, i.e.…”

Critical Condition in CuInAlSe2 Growth of Solar Cell Absorber

“…The small grains meant that the film had large grain boundaries with relatively low electronic activity [28]. [29,30]. Materials could include insulators, semiconductors, and conductors depending on the band gap energy between the valence and conductive bands.…”