Ag–Al alloy thin film on plastic substrate by screen printing for solar cell back contact application

Ag–Al alloy thin films with different thicknesses were screen printed onto polyethylene terephthalate plastic substrates at room temperature. Three different weights of pure Ag paste were mixed with Al paste to create alloy pastes with different viscosities. A uniform composition of Ag and Al was obtained with a 70:30 composition ratio. The variation in the viscosity of the mixed paste enabled production of different thicknesses of printed layers. The deposited films were annealed at 200 °C for 45 min. Structural characterization and elemental content analysis of the films were carried out using X-ray diffraction (XRD), Raman spectroscopy, and energy-dispersive X-ray spectroscopy. The surface morphology of the printed films was studied by scanning electron microscopy and atomic force microscopy. Their electrical properties were investigated by four-point probe measurements. The crystalline sizes and strain along the a and c axes were calculated from the XRD patterns. Both were found to increase with increased film thickness.