Post-selenization tailored carrier-crystallographic synergy in c-axis Bi₂Se₃ thin films for advanced thermoelectrics

Bi₂Se₃ has emerged as a promising thermoelectric (TE) material due to its environmentally benign composition and earth-abundant constituents. However, the practical implementation of Bi₂Se₃-based systems remains challenging due to suboptimal TE performance. This study demonstrates the fabrication of c-axis oriented Bi₂Se₃ thin films through pulsed laser deposition, with subsequent selenization treatment significantly enhancing TE performance through dual optimization of carrier concentration and crystallographic alignment. A strategic post-deposition selenization process effectively mitigates selenium vacancies and correspondingly reduces the carrier concentration to 2.0 × 10¹⁹ cm⁻³ while improving in-plane carrier mobility. A high power factor (PF) of about 9.5 μW·cm⁻¹·K⁻² is achieved at 475 K in the highly c-axis oriented Bi₂Se₃ thin films selenized for about 60 min, outperforming the reported state-of-the-art Bi₂Se₃ films. Demonstrating practical applicability, an 8-leg planar thin-film device generates an exceptional power density of 441.3 μW/cm² under a 25 K temperature gradient, establishing new performance benchmarks for chalcogenide-based microgenerators. These findings provide crucial insights into defect engineering and structural optimization strategies for developing high-performance TE devices compatible with self-powered microelectronic applications.