P型碲化鉍熱電薄膜的雷射退火技術於柔性能源採集裝置之應用

Abstract

隨著穿戴式電子設備的快速發展，對於具有輕薄、可撓與低功耗特性的微型發電模組需求日益增加，而熱電元件作為一種可直接將熱能轉換為電能的技術，展現出應用於能源回收與自供電裝置的潛力。然而，傳統製程裡的高溫退火難以直接應用於柔性基版上。為解決此問題本研究以磁控濺鍍機在柔性PET基板上沉積P型碲化鉍薄膜，並透過532 nm連續波雷射進行大氣環境下之退火，探討不同雷射製程參數對薄膜熱電性能之影響，並成功製作出柔性能源採集裝置。 研究中藉由改變雷射強度、掃描速度、線重疊率及掃描次數等參數，研究薄膜退火的能量閾值、電性、微觀結構與熱電性質。在最佳參數條件下，能在不損壞薄膜的情況下，將電導率由未退火之11.3 S/cm提升至980.4 S/cm，增幅達87倍；遷移率從2.8 cm^2/Vs增加至46.4 cm^2/Vs，載子濃度也提升至1.32×10^20 cm^-3。熱電性質方面，席貝克係數由66 μV/K 增至183 μV/K，提升約2.8倍；功率因數由0.05 μW/cmK^2增至23 μW/cmK^2，提升超過460倍，顯示雷射退火後碲化鉍晶粒成長，晶體缺陷密度大幅降低。夾層設計的柔性元件有效降低彎曲對薄膜負面的影響在彎曲測試中，經過1000次、彎曲半徑8 mm的彎曲循環後，電導率仍維持初始值之88%，展現良好之可撓性。 本研究成功實現一項快速、低熱損且可於大氣環境中退火柔性基板上的碲化鉍薄膜之技術，在經過功率因數最佳化後，具有應用於柔性微型熱電元件的潛力，為將來能源回收與永續願景帶來貢獻。

With the rapid development of wearable electronic devices, there is an increasing demand for lightweight, flexible, and low-power micro energy harvesting modules. Thermoelectric generators, which directly convert heat into electricity, have emerged as promising candidates for energy recycling and self-powered systems. However, conventional high-temperature annealing processes are difficult to apply directly on flexible substrates. To address this issue, this study employed magnetron sputtering to deposit P-type bismuth telluride thin films on flexible PET substrates, followed by annealing using a 532 nm continuous-wave laser under ambient conditions. The effects of various laser processing parameters on the thermoelectric properties of the films were systematically investigated and a flexible energy harvesting device was successfully fabricated. By varying laser intensity, scanning speed, line overlap ratio, and scan times, the study examined the annealing energy threshold, electrical performance, microstructure, and thermoelectric characteristics of the films. Under optimal conditions, the electrical conductivity increased from 11.3 S/cm to 980.4 S/cm, representing an 87 times enhancement. The carrier mobility rose from 2.8 to 46.4 cm²/Vs, and the carrier concentration reached 1.32 × 10²⁰ cm⁻³. In terms of thermoelectric performance, the Seebeck coefficient increased from 66 μV/K to 183 μV/K, and the power factor improved dramatically from 0.05 to 23 μW/cm·K²—an enhancement of over 460 times—indicating significant grain growth and reduced defect density due to laser annealing. Furthermore, the layered design of the flexible device effectively mitigated the adverse effects of bending on the thin film. After 1000 bending cycles at a radius of 8 mm, the electrical conductivity retained 88% of its initial value, demonstrating excellent flexibility. This study successfully demonstrated a rapid, low-thermal-budget laser annealing method for Bi2Te3 thin films under ambient conditions. The optimized power factor performance highlights the potential of this technique for application in flexible micro thermoelectric generators (µ-TEGs), contributing to future energy harvesting and sustainability goals.