電極材料對薄膜碲化鉍熱電模組性質之影響;Effect of Electrode Materials on Thermoelectric Property for Bi2Te3 Thin Film Thermoelectric Module

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题名:	電極材料對薄膜碲化鉍熱電模組性質之影響;Effect of Electrode Materials on Thermoelectric Property for Bi2Te3 Thin Film Thermoelectric Module
作者:	鄭凱文;Cheng, Kai-Wen
贡献者:	化學工程與材料工程學系
关键词:	碲化鉍;薄膜模組;擴散行為;反位缺陷;熱電性質;Bi2Te3;Thin film module;Diffusion behavior;Antisite defect;Thermoelectric property
日期:	2023-08-07
上传时间:	2024-09-19 14:47:52 (UTC+8)
出版者:	國立中央大學
摘要:	近年來，隨著環保的意識抬頭與減少碳排放量的共識，綠色能源的發展正如火如荼的進行中。其中，熱電裝置作為一種環境友善的熱能與電能轉換技術，沒有任何移動部件，能在安靜且穩定的特性下將廢熱轉換為電能。在薄膜熱電模組中，熱電材料時常因兩端電極的擴散而大幅影響模組本身的性能，在實際應用下模組更會進行長時間的熱時效處理，其造成的擴散行為對於整體模組的影響更為重大。本研究以共濺鍍之高結晶取向Bi2Te3材料作為熱電薄膜，並以電導率較高之Cu和Ni作為金屬電極，探討Cu/Bi2Te3/Cu和Ni/Bi2Te3/Ni模組在長時間熱時效處理下，不同電極的擴散行為以及其界面穩定性，在Cu/Bi2Te3/Cu模組中，Cu原子藉由表面及晶界的擴散遷移至Bi2Te3薄膜中，擴散後的Cu原子在Bi2Te3薄膜的晶界中析出，並在Bi2Te3薄膜的表面上生成Cu2−xTe介金屬化合物 (IMC)，其接觸電阻隨著熱時效處理的時間增加而大幅上升。然而，在Ni/Bi2Te3/Ni模組中，雖然Ni原子僅擴散進Bi2Te3薄膜約50奈米處，並無任何IMC生成在界面處，但Ni原子的擴散仍使接觸電阻有著明顯的上升。在長時間熱時效處理下，使得原始的Bi2Te3薄膜與Ni/Bi2Te3/Ni模組中生成Bi_Te^·反位缺陷，其部分熱電薄膜由原本的n-型Bi2Te3轉變為p-型Bi2Te3，進而使其整體功率因子降低。綜合Cu/Bi2Te3/Cu和Ni/Bi2Te3/Ni模組的擴散行為以及熱電性質，Cu/Bi2Te3/Cu模組顯示Cu原子的擴散顯著地減緩Bi2Te3薄膜的功率因子在長時間熱時效處理下的衰退。;With the increase in environmental awareness and the consensus to reduce carbon emissions, the development of effective energy harvester is an inevitable trend. A thermoelectric device, as an eco-friendly and solid-state energy converter, is silent and reliable because it has no moving parts, and can directly convert waste heat into electric energy. For thin film thermoelectric modules with electrodes deposited on the sides of the thermoelectric material, the diffusion of atoms from the electrode affects the module’s performance. Long-term aging is crucial when the module is for practical applications. In this study, Bi2Te3 thin films with a highly preferred orientation were fabricated by co-sputtering deposition method. Cu and Ni were used as the electrodes because of their high electrical conductivity. The diffusion behavior and interfacial stability of the Cu/Bi2Te3/Cu and Ni/Bi2Te3/Ni samples were investigated by long-term aging. Cu migrates through the Bi2Te3 film via surface and grain boundary diffusion. The diffusing Cu segregates at grain boundaries and forms a Cu2−xTe intermetallic compound on the sample surface. Contact resistivity at the interface between the Cu electrode and Bi2Te3 thin films substantially increases with aging time. However, although Ni only diffuses into the Bi2Te3 layer by approximately 50 nm, the penetration of Ni still deteriorates the contact resistance of thin film thermoelectric modules. Long-term aging unavoidably degrades the power factor (PF) of the pristine Bi2Te3 and Ni/Bi2Te3/Ni samples since n-type Bi2Te3 converts into p-type by the formation of Bi_Te^· antisite defects. The study shows that the diffusing Cu from the electrodes of the Cu/Bi2Te3/Cu module significantly mitigate the degradation of the PF after long-term aging.
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