We report the fabrication of a flexible network of multiwall carbon nanotubes (MWCNTs) known as buckypaper (BP) for thermoelectric (TE) applications. A thermal evaporation method was used to deposit TE metal alloys onto the BP. The TE properties were improved primarily by increasing the Seebeck coefficient values (50 and 75？μV/K) and the electrical conductivity by approximately 10？000？S/m. High-temperature resistivity studies were performed to confirm the semiconductivity of buckypaper. Variations in resistivity were observed to be the result of the metal alloys coated on the BP surface. We also demonstrated that a substantial increase in the Seebeck coefficient values can be obtained by connecting 3 and 5 layers of metal-deposited BP in series, thereby enhancing the TE efficiency of MWCNT-based BP for application in thermoelectric devices. 1. Introduction Recently, a considerable amount of effort has been devoted to developing thermoelectric (TE) devices that are capable of generating electricity from heat. TE devices that conserve heat energy should be cost-efficient and possess a high thermoelectric figure of merit [1]. Good TE materials must have a high Seebeck coefficient, which enhances thermoelectricity, low electrical resistivity, which minimizes Joule heating, and low thermal conductivity, which sustains a large temperature gradient [2]. The performance of a TE material is determined by its dimensionless figure of merit , where , , and are the Seebeck coefficient, electrical resistivity, and thermal conductivity of the materials, respectively. Previous studies have focused on semimetallic nanomaterials such as Bi, Sb, Te, and Bi-Sb alloys because of their promising thermoelectric properties [3–5]. Bi2Te3-based alloys are known to be a state-of-the-art material currently available for TE applications [6]. Recently, Zhang et al. [7] reported that the Seebeck coefficient of Bi2Te3 can be improved by incorporating single wall carbon nanotubes (SWCNTs) into the matrix. Furthermore, highly doped SWCNTs can be used to tune Bi2Te3 from - to -type. Despite their excellent thermoelectric properties, these materials exhibit poor mechanical property, which complicates the fabrication process, and can cause reliability problems in their application, especially in miniature TE modules. Recently, there has been considerable focus on macroscopic assemblies of various carbon nanotubes (CNTs) such as buckypaper (BP), fibers, pellets, and thin films because the characteristics of a single CNT can be used on a macroscopic scale to fabricate reliable,
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