Photovoltaic device performance of pure, manganese (Mn2+) doped and irradiated CuInSe2 thin films.

Pure and Mn²⁺ doped CuInSe₂ thin films (Mn content: 1 to 5 mole%) were deposited on indium doped tin oxide (ITO) glass substrates by a single step electrochemical deposition method at low temperature (358 K). The as-deposited pure CuInSe₂ thin films were irradiated with Au⁸⁺ ions (100 MeV) at room temperature and liquid nitrogen temperature with an ion fluency of 1 × 10¹⁴ ions per cm². Glancing angle X-ray diffraction patterns showed that the as-deposited pure and Mn²⁺ doped CuInSe₂ thin films and the irradiated thin films have a tetragonal crystal structure without any trace of secondary phases. Mn²⁺ doping does not alter the tetragonal structure of CuInSe₂ thin films except for a strong (112) plane preferred orientation in all the doped thin films. The absorption coefficient's fall is sharper for 5 mole% Mn²⁺ doped and irradiated CuInSe₂ thin films than for pure and 1 to 4 mole% Mn²⁺ doped CuInSe₂ thin films due to better crystallinity. Magnetic measurements reveal that Mn²⁺ doping into the CuInSe₂ lattice induces ferromagnetism. The electrical studies of Mn²⁺ doped and irradiated CuInSe₂ thin films show that hole mobility and hole concentration increase with a slight decrease in resistivity. Mn²⁺ in CuInSe₂ thin films acts as an acceptor and the original p-type conductivity is retained. The new antistructural modeling for describing the defects in the CuInSe₂:Mn system shows that the dissolution of the Mn cations in the chalcopyrite matrix increases the hole concentration. Solar light irradiation with an intensity of 100 mW cm⁻² on Mn²⁺ (5 mole%) doped and LNT irradiated CuInSe₂ thin film-based cells resulted in a power conversion efficiency of 6.38 and 4.57%, respectively. [ABSTRACT FROM AUTHOR]