The effect of Al and In concentrations on the properties of electrodeposited Cu(In,Al)Se2 using two electrode system without the addition of complexing agents

Abstract

Chalcopyrite Cu(In,Al)Se2 thin films were deposited by electrodeposition process onto ITO coated glass substrates from de-ionized water solution consisting of CuCl2, InCl3, AlCl3 and SeO2 precursors. The effect of Al and In concentrations in precursor solutions on the properties of Cu(In,Al)Se2 films were investigated by varing x ratio (x=[Al]/[In+Al]) from 0 to 0.75. The structural, optical and electrical properties of films were studied, respectively, using X-ray diffraction, Raman spectroscopy, UV-visible spectrophotometer, Hall-effect and four-point probe method. The X-ray diffraction analysis proved that the film deposited at x=0.75 present Cu(In,Al)Se2 single phase in its chalcopyrite structure and with preferred orientation along [112] direction, however the others films show the main Cu(In,Al)Se2 chalcopyrite with the formation of In2Se3 as a secondary phase.The band gap energy of the films was controlled from 1.17 to 1.65eV by adjusting the Al and In concentrations in the precursor solutions. The Raman analysis revealed that all the films mainly consist of a chalcopyrite structure and the film deposited at x=0.25 contain the ternary compounds CuAlSe2 as secondary phase. This last film showed n-type conduction while the rest of the films showed p-type conduction. The electrical resistivity is in the range of 0.06–1.9Ωcm.