The I-III-VI2 compounds are direct energy-gap semiconductors showing very interesting electrical and optical properties. Solar cell technologies using Cu-III-VI2, especially CuInGaSe2 (CIGS), based solar cells have been extensively reported, primarily because of its large absorption coefficient and its bandgap energy of between 1.0 and 1.7 eV at room temperature. Conversion efficiencies for polycrystalline CIGS based solar cells have been significantly improved over recent years and the best cell is now reported at 19.5 % [1]. AgInSe2 material is a chalcopyrite semiconductor and has a high absorption coefficient because of direct band gap structure. This is expected as solar cell absorber. An efficiency of energy conversion of more than 6% has been reported recently on p-AgInSe2/n-CdS [2]. However, the material characterization on AgInSe2 is not well understood.
In this work, the undoped AgInSe2 crystals are grown by hot-press (HP) method at 400 ~ 700 °C for 1 h under high pressure (10 ~ 40 MPa). One of the advantages of the HP method is that a crystal growth is easy at low temperature. The sizes of the samples are 2 cm in diameter. All samples indicate chalcopyrite structures, nearly stoichiometry and n-type by means of X-ray diffraction, electron probe microanalysis and thermoprobe analysis, respectively. However, the sample grown at 400 °C has a secondary phase. According to increasing temperatures, the sample does not have the secondary phase. A single phase AgInSe2 crystal can be successfully obtained at 700 °C.
[1] M. A.Contreras, K. Ramanathan, J. Abushama, F. Hasoon, D. L. Young, B. Egaas and
R. Noufi, Prog. Photovol. Res. Appl. 13 (2005) 209.
[2]P. P. Ramesh, O. M. Hussain, S. Uthanna, B. S. Naidu and P. J. Reddy: Mater. Lett. 34
(1997) 27.
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