Structural, Optical, Electrical, Thermoelectric and Photoelectrochemical Properties of Nanoscale Silver Bismuth Selenide Thin Films

Silver bismuth selenide thin films were prepared and examined to understand their structural, optical, compositional, electrical, and thermoelectric behavior. X-ray diffraction analysis verified the formation of a phase pure hexagonal structure with good crystallinity and preferred orientation. The scanning electron images reveal a dense and continuous film composed of uniformly distributed nanoscale crystallites, with sizes ranging approximately 18–25 nm. Optical characterization showed strong absorption across the visible to near-infrared spectral region, and the optical band gap determined from Tauc plots lies within a range favorable for optoelectronic and energy-conversion applications. Electrical transport measurements revealed temperature dependent semiconducting behavior. Thermoelectric investigations conducted over the temperature range of 300–525 K exhibited a negative Seebeck coefficient throughout, indicating n-type charge transport. The Seebeck coefficient increased from 80.46 μV K–1 at 300 K to 105.49 μV K–1 at 525 K. With increasing temperature, the carrier concentration rose from 1.1 × 1019 to 1.9 × 1019 cm–3, while the carrier mobility improved from 0.3 to 0.9 cm2 V–1 s–1. The enhancement in mobility is attributed to the weakening of grain-boundary potential barriers at elevated temperatures. The corresponding fill factor was 0.48, resulting in a photoelectrochemical conversion efficiency of approximately 1.02%.