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Journal of Physical Studies 22(4), Article 4602 [4 pages] (2018)
DOI: https://doi.org/10.30970/jps.22.4602 OPTICAL PROPERTIES OF THIN CRYSTALLINE FILMS CuIn0.5Ga0.5Se2 OBTAINED BY LASER DEPOSITIONR. V. Gamernyk1, Yu. O. Plevachuk1, V. M. Sklyarchuk1, І. S. Virt2, Yu. О. Kulyk1
1Ivan Franko National University of Lviv |
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Thin-film solar cells based on chalcopyrite are promising for terrestrial and space applications. The CuInSe$_2$ semiconductor (CIS) has a band gap of about 1.04 eV, which is somewhat smaller than the ideal value for photovoltaic solar cells. Adding Ga to CIS in order to form the CuIn$_{1-x}$Ga$_x$Se$_2$ compound (CIGS) increases the band gap width, bringing it closer to the ``ideal''; increases the idle voltage but reduces the short-circuit current. However, until now the effects of Ga admixtures remain unknown. It was reported that acceptor levels in crystals CIS and CIGS are identical and donor levels in CIGS are deeper than in CIS. Therefore, doping with CIGS crystals is more difficult than with CIS crystals. Obviously, further progress in the implementation of such devices can be achieved using new technologies for producing thin films with reproducible and controllable physical parameters. In this study, crystal films CuIn$_{0.5}$Ga$_{0.5}$Se$_2$ were obtained by laser deposition on dielectric substrates from pre-synthesized crystals. The size of the crystallites based on SEM images does not exceed 50 nm. The parameters of the tetragonal cell of the solid solution were determined and the linear increase of the tetragonal parameter was recorded. The $p$-type conductivity of the material was determined by the method of measuring the photodiffusion current. In the case of intensive zone-zone excitation, an emission of bound excitons from nanosized crystallites has been registered. The origin of the features of the thin-film photoluminescence spectra has been analyzed.
PACS number(s): 64.70.Ja, 64.75.+g, 66.20.+d