Electrosynthesis and Characterizations of Aluminum Silver Selenide (Alagse2), Thin Films for Possible Device Applications

The semiconductor thin films of Aluminum Silver selenide (AlAgSe2) have been successfully deposited onto FTO glass substrate using electrodeposition method. AgNO3, AlCl3.6H2O and Selenium powder were the precursors used for sources of Ag, Al and Se ions respectively. Prototype of the films were again made and subjected to annealing at temperature of 150°C for 5 minutes to remove the element of moisture content in the as deposited films. The properties of the films such as optical, structural and compositional were investigated using UV-VIS Spectrophotometry, X-ray diffractometry and Rutherford Backscattering Spectroscopy (RBS) analysis respectively to determine the possible areas of applications of the films. Optical analysis revealed that the films have high absorbance in the UV region but decreased in the visible and near infrared regions. The increase in the concentration of selenide ions however decrease the absorbance of the films but annealing tends to increases the absorbance. The films also exhibited very high values of refractive index with minimum value in the order of 2.0 for both the annealed and as deposited samples. The bandgap energies of the films were found to be 1.7 eV, 1.8 eV, 2.2 eV, 2.8 eV and 2.9 eV for as deposited, but decreased to the values of 1.5 eV, 1.6 eV, 1.92 eV, 2.15 eV and 2.5 eV after annealing for the films deposited with 0.1 M, 0.2 M, 0.3 M, 0.4 M and 0.5 M Se ions respectively. The structural analysis indicates that AlAgSe2 films are crystalline in nature with most preferential crystalline plane of (112). The RBS compositional analysis showed that the deposited thin films are rich in silver content. These properties exhibited by the deposited thin films of AlAgSe2 are desirable for photovoltaic devices and for many other optical and optoelectronic applications.