Wang Bo, Li Yu, Zheng Jiaxin, Xu Ming, Liu Fusheng, Ao Weiqing, Li Junqing, Pan Feng
College of Materials Science and Engineering, Shenzhen University and Shenzhen Key Laboratory of Special Functional Materials, Shenzhen 518060, People's Republic of China.
School of Advanced Materials, Peking University, Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
Sci Rep. 2015 Mar 20;5:9365. doi: 10.1038/srep09365.
Serials of Ga doping on Sn sites as heterovalent substitution in Cu2CdSnSe4 are prepared by the melting method and the spark plasma sintering (SPS) technique to form Cu2CdSn(1-x)GaxSe4 (x = 0, 0.025, 0.05, 0.075, 0.01, and 0.125). Massive atomic vacancies are found at x = 0.10 by the heterovalent substitution, which contributes significantly to the increase of electrical conductivity and the decrease of lattice thermal conductivity. The electrical conductivity is increased by about ten times at 300 K after Ga doping. Moreover, the seebeck coefficient only decreases slightly from 310 to 226 μV/K at 723 K, and a significant increase of the power factor is obtained. As a result, a maximum value of 0.27 for the figure of merit (ZT) is obtained at x = 0.10 and at 723 K. Through an ab initio study of the Ga doping effect, we find that the Fermi level of Cu2CdSnSe4 is shifted downward to the valence band, thus improving the hole concentration and enhancing the electrical conductivity at low doping levels. Our experimental and theoretical studies show that a moderate Ga doping on Sn sites is an effective method to improve the thermoelectric performance of Cu2CdSnSe4.
通过熔融法和放电等离子烧结（SPS）技术制备了一系列在Cu2CdSnSe4中Sn位点上进行Ga掺杂作为异价取代的样品，以形成Cu2CdSn(1 - x)GaxSe4（x = 0、0.025、0.05、0.075、0.10和0.125）。通过异价取代发现在x = 0.10时存在大量原子空位，这对电导率的增加和晶格热导率的降低有显著贡献。Ga掺杂后，300 K时电导率增加了约十倍。此外，塞贝克系数在723 K时仅从310略微下降到226 μV/K，并且功率因数显著增加。结果，在x = 0.10和723 K时获得了优值（ZT）的最大值0.27。通过对Ga掺杂效应的第一性原理研究，我们发现Cu2CdSnSe4的费米能级向下移动到价带，从而在低掺杂水平下提高了空穴浓度并增强了电导率。我们的实验和理论研究表明，在Sn位点上进行适度的Ga掺杂是提高Cu2CdSnSe4热电性能的有效方法。
