Amorphous Framework in Electrodeposited CuBiTe Thermoelectric Thin Films with High Room-Temperature Performance

Abstract

Bismuth telluride-based alloys are the most efficient thermoelectric materials near room temperature and widely used in commercial thermoelectric devices. Nevertheless, their thermoelectric performance needs to be improved further for wide-scale implementation either as a thermoelectric generator or cooler. Here, we propose a simultaneous codeposition of CuBiTe thin films and their phase transition strategy via the traditional electrodeposition process. With just 13 atom % Cu doping, crystalline-to-amorphous phase transformation resulted for the electroplated CuBiTe alloy. A close look at the alloy composition revealed spike-shaped nanocrystalline Bi 2 Te 3 embedded in the CuBiTe amorphous matrix. Our result shows an exceptionally high power factor (3.02 mW m –1 K –2 ), which comes from the enhanced Seebeck coefficient (−275 μV K –1 ) and high electrical conductivity (3.99 × 10 4 S m –1 ) of CuBiTe films. Therefore, it can be suggested that the adopted strategy to form a unique nanocrystallite-embedded amorphous framework provides a platform to develop next-generation high-performance thermoelectric materials with an extraordinary power factor.

Electrodeposited CuSbTe thin films with enhanced thermoelectric performance

“…35,36 The film is strongly orientated in the (110) direction as compared to the (015) direction and can be indexed to the corresponding standard pattern of the crystalline Sb 2 Te 3 hexagonal closed pack layered structure (JCPDS #01-072-1990). The other peak at 38° is due to the Au seed layer used for the electrodeposition, 20 which is observed in each film. In the case of ternary Cu0·2SbTe, the preferential orientation of the (110) plane disappears, and only a less intense (015) orientation is observed, indicating that Cu co-deposition inhibits the growth of Sb 2 Te 3 crystallites at the (110) plane.…”

“…The CVs are generally similar in shape as the Cu concentration increases, but the reduction peaks shift towards the positive direction, indicating the formation of Cu + or Cu 2+ . The deposition of CuSbTe can be expressed by the following equation: 20 n Cu + + 2 n e − + 2Sb 3+ + 3Te 2+ ↔ Cu n Sb 2 Te 3 + n e − …”

“…19 Electrodeposition is a highly productive and adaptable method that offers high deposition rates, scalability, ease of operation, low cost, and precise control over a variety of parameters such as composition and morphology. 6 Padmanathan et al reported that increasing the Cu content in electrodeposited CuBiTe 20 or even in the Te film 21 improved the power factor. The Cu-doping reduced the carrier concentration, leading to a larger Seebeck coefficient at room temperature.…”

“…29 As a result of increased vacancy concentration, the power factor is greatly enhanced. 20 However, the mechanism involved in Cu co-deposition and the formation of an amorphous ternary alloy is not clear yet. In addition, it is very challenging to investigate their intrinsic thermoelectric characteristics along with the base crystallite structure.…”

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“…Bi2Te3-based materials are the most sophisticated thermoelectric materials on the market, notably at room temperature [12][13][14][15][16][17][18][19][20]. Increasing the concentration of point defects in a material is an effective technique to reduce its thermal conductivity, especially for phonons in the high frequency band [4].…”