High thermoelectric performance of high‐mobility Ga‐doped ZnO films via homogenous interface design

Abstract

Ga-doped ZnO (GZO) thin films grown on sapphire substrates have been widely investigated as a promising transparent thermoelectric (TE) material. However, due to the large lattice mismatch and thermal expansion between the sapphire substrate and GZO film, strain-induced lattice distortion impedes the transport of electrons, leading to low carrier mobility. In this study, ZnO homo-buffer layers with different thicknesses were inserted between sapphire substrates and GZO films, and their effect on the TE properties was investigated. A thin ZnO interlayer (10 nm) effectively reduced the lattice mismatch of the GZO film and improved the carrier mobility, which contributed to the large enhancement in the electrical conductivity. Simultaneously, energy filtering occurred at the interface between GZO and ZnO, resulting in a relatively high density of states (DOS) effective mass and maintaining a high Seebeck coefficient compared to that of the unbuffered GZO films. Consequently, the GZO film with a 10 nm thick ZnO buffer layer possessed a high power factor value of 449 μW m −1 K −2 at 623 K. This study provides a facile and effective method for optimizing the TE performance of oxide thin films by synergistically improving their carrier mobility and enhancing their effective mass.

Optimized weighted mobility induced high thermoelectric performance of ZnO‐based multilayered thin films

“…(A) Temperature‐dependent power factor (PF) of D‐ZnO/gallium‐doped zinc oxide (GZO), H‐ZnO/GZO, and O‐ZnO/GZO thin films (as deposited and as annealed GZO thin films were taken from our previous work 16,17 for comparison); (B) comparison of average power factor (PF ave ) value in the temperature ranges from 300 to 623 K for O‐ZnO/GZO thin film in this work and n‐type oxygen‐containing thermoelectric materials from our previous work and Refs. [13, 16, 17, 28–33]…”

“…Considering the low cost, good chemical, and thermal stability as well as transparency, gallium‐doped zinc oxide (GZO) thin films have been widely investigated 12–15 . Our previous work indicated that constructing ZnO–GZO interfaces could effectively optimize the electrical properties of GZO thin films due to energy filtering effects that occurred at the interfaces 16,17 . However, the designed structures only contained one ZnO layer and formed one or two ZnO–GZO interfaces.…”

“…[12][13][14][15] Our previous work indicated that constructing ZnO-GZO interfaces could effectively optimize the electrical properties of GZO thin films due to energy filtering effects that occurred at the interfaces. 16,17 However, the designed structures only contained one ZnO layer and formed one or two ZnO-GZO interfaces. Thus, we are wondering if more ZnO-GZO interfaces would bring much better thermoelectric performance.…”

Enhancing Thermoelectric Properties of (Cu2Te)1−x-(BiCuTeO)x Composites by Optimizing Carrier Concentration

“…Therefore, TE materials with high power factor (PF), which is defined as , but low thermal conductivity, are suitable for thermoelectric applications. To get the ideal thermoelectric performance, the PF of materials can be raised by band engineering, quantum confinement effects and electron energy barrier filtering [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Besides, can be reduced by nanostructures all-scale hierarchical architecture engineering, which is able to increase the scattering of short, medium and long wavelength phonons, and entropy engineering [ 17 , 18 , 19 , 20 , 21 , 22 ].…”

The Influence of Sb Doping on the Local Structure and Disorder in Thermoelectric Zno:Sb Thin Films

“…For example, regarding ZnO-based nanostructured ceramic pellets at 300 K, there are reports of absolute Seebeck coefficients of ∼500 μV/K for ZnO:Bi and ZnO:Al, ∼300 μV/K ZnO:In, and ∼200 μV/K for ZnO:Ga [14,16,19,20]. As a comparison, much smaller absolute Seebeck coefficients have been obtained at 300 K for doped-ZnO transparent thin films deposited at low temperature (< 473 K): ZnO:Al (∼35 μV/K), ZnO:Ga (∼30 μV/K), ZnO:Sb (∼25 μV/ K), ZnO:Al,Bi (∼50 μV/K), ZnO:Ga,Bi (∼40 μV/K), ZnO:Sb (40-60 μV/K) [17,18,21,22].…”