Optimization of AgBiS₂ nanostructure thin film for photovoltaic applications

AgBiS₂ (ABS), a ternary chalcogenide compound (I-V-VI) with its high absorption coefficient and tunable bandgap energy, shows as a potential alternative material to hazardous chalcogenides. While notable progress has been made in fabricating ABS thin films through solution processes, so far not much work has been reported on physical techniques. This study reports the successful optimization of phase-pure cubic ABS films using thermal-vapor deposition from a single-target bulk cubic ABS source. ABS thin films were deposited onto cleaned glass substrates at ambient temperature under a base chamber vacuum pressure 10^-5 mbar. The as-prepared ABS thin films were post-annealed at various temperatures (200^oC, 220^oC, 240^oC, 260^oC) in an Argon environment and subjected to sulfurization. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) confirm the phase-pure cubic ABS thin films. The samples result a high absorption coefficient (10⁵ cm^-1), and the bandgap energies were estimated to 1.0 - 1.3 eV. The surface morphology analyzed by field-emission scanning electron microscopy (FESEM), and the average grain size is calculated ≅ 35-45 nm. FESEM coupled with electron dispersive X-ray spectroscopy (EDS) estimated the atomic percentage of the samples. The I-V characteristics of the devices are measured using AM1.5G solar simulator. The ABS films showed a promising potential for optoelectronic/photovoltaic devices.