Synthesis and characterization of AgInTe ₂ thin films: role of annealing on phase formation and optoelectronic properties

This study adopts a systematic approach to realize high-quality single-phase AgInTe₂thin films and investigates their properties for potential use as an absorber material in photovoltaic devices. The films were prepared by vacuum deposition of stacked elemental layers (SELs) (In/Te/Ag) × 3 on glass substrates at 100 °C, followed by annealing in an inert atmosphere. The formation of AgInTe₂films, from annealing of SELs (In/Te/Ag) × 3, and properties of AgInTe₂films were extensively unveiled using various analytical tools and discussed with respect to annealing temperature and duration. Based on a comprehensive study, an annealing temperature of 450 °C and an annealing duration of 90 min were found to be optimal for obtaining single phase AgInTe₂films. X-ray diffraction analysis reveal that the AgInTe₂films had a tetragonal crystal structure. This film shows a single-phase AgInTe₂crystal structure with uniform and compact surface morphology having an average grain size of 450 nm. Secondary ion mass spectrometry confirmed a homogeneous distribution of Ag, In and Te throughout the film's thickness. Optical analysis identified two distinct band gaps:<i>E</i>_g1= 1.02 eV, corresponding to the fundamental interband transition, and<i>E</i>_g2= 1.10 eV, related to a crystal field-induced valence band splitting. Spectroscopic ellipsometry (SE) provided precise measurements of optical constants (<i>n, k</i>) and dielectric functions of the films. Electrical analysis resulted in<i>p</i>-type conductivity of the films with the highest carrier concentration of 2.41 × 10¹⁵cm^-3, a mobility of 214.7 cm²V^-1s^-1,and a resistivity of 12 Ω cm. The findings suggest that AgInTe₂holds significant potential as an absorber material for heterojunction thin film solar cells.