Copper selenide (Cu 2 Se) has been extensively studied as an eco-friendly thermoelectric candidate owing to the outstanding thermoelectric performance of its high-temperature β-phase. In this study, we propose that α-Cu 2 Se is also a promising thermoelectric material at near-room-temperature. We synthesize nanostructured Cu 2-x Se via a facile solvothermal method, and densify the samples using Spark Plasma Sintering to maintain the small grain sizes. Although the as-prepared α-Cu 2 Se has intrinsically low lattice thermal conductivity , its high Cu deficiency leads to a high carrier concentration, therefore, a low thermoelectric performance. As an electron donor, bismuth can effectively compress the Cu vacancies of the as-prepared α-Cu 2 Se and in turn reduce its carrier concentration from 4.1 × 10 20 to 2.0 × 10 20 cm −3 at room temperature, achieving a significantly enhanced power factor and a reduced carrier thermal conductivity. Consequently, a zT of 0.43 at 373 K is obtained in Cu 1.982 Bi 0.006 Se, showing great potential in developing high-performance near-room-temperature α-Cu 2 Se-based thermoelectric materials.
Jiahui Li,Jie Gao,Lida Jia,Lei Miao,Sijing Zhu,Zhongwei Zhang,Chengyan Liu,Xiaoyang Wang
The solution-process method can be easily realized without expensive and complicated equipment, which provides the possibility for cost-effective application of flexible thermoelectric films. Nonetheless, the reported output properties of solution-processed Cu 2 Se based films are not satisfactory due to the absence of effective compositional adjustment and optimal length. In this work, a series of solution-processed nylon-supported flexible Cu 2+x Se films have been fabricated. The excess Cu not only fills the vacancies, but also transforms the β -Cu 2 Se with disordered Cu atoms into long-range ordered lamellar α -Cu 2 Se, thereby reducing the carrier concentration and improving the carrier mobility of the films. As a result, a high power factor of 856.59 ± 119.92 μW m −1 K −2 has been achieved in the Cu 2.20 Se film at 303 K. In addition, by numerical simulation, the ideal length of single Cu 2.20 Se film was calculated to be 2 mm. With an actual temperature difference of 6.6 K, a maximum output power density of 2.918 μW cm −2 K −2 , which is superior to those of other p-type flexible thermoelectric films, is realized in the single Cu 2.20 Se film. This work provides a feasible idea to promote the output performance of solution-processed flexible thermoelectric films.
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