The Effect of Sputtering Power on the Properties of One-step Deposited Cu 2 ZnSnSe 4 Thin Films
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The Effect of Sputtering Power on the Properties of One-step Deposited Cu2ZnSnSe4 Thin Films Yong Yan1, Shasha Li1, Zhou Yu1, Yong Zhang1, Yong Zhao1,2 1 Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle, Ministry of Education of China, Superconductivity and New energy R&D Center (SNERDC), Southwest Jiaotong University, Chengdu 610031, China. 2 School of Materials Science and Engineering, University of New South Wales, Sydney 2052 NSW, Australia.
ABSTRACT Cu2ZnSnSe4 films were deposited on soda lime glass substrates at room temperature by onestep radio frequency magnetron-sputtering process. The effect of sputtering power on the properties of one-step deposited Cu2ZnSnSe4 thin films has been investigated. The deposited films might be suitable for the absorber layers in the solar cells. The chemical composition and the preferred orientation of the films can be optimized by the sputtering power. INTRODUCTION It is known that the limited availability of fossil fuels and environmental problems associated with them have set off the search for other forms of energy generation. Among these forms, solar power generation emerge as the most promising clean energy solution. Recently, thin film solar cells made of Cu(In, Ga)Se2 and CdTe have record conversion efficiencies of 20.4% [1] and 18.7%[2], respectively. Nevertheless, there are concerns about their large-scale production due to the increasing price of mineral resources: Indium, Gallium and Tellurium. Quaternary compound semiconductor Cu2ZnSnSe4 is regarded as a promising candidate for the next generation solar cells owing to the relative abundance of the component elements and its suitable band gap for the absorber layers. CZTSe can crystallize in kesterite and stannite structure, these two phases can coexist in experimental samples prepared by various methods. However, there are still many challenges to synthesize high-quality single-crystal samples. The biggest problem is the coexistence of secondary phases [3, 4]. Many researchers have reported that the solar cell short-circuit current density is limited by the formation of a current blocking ZnSe phase toward the front contact [3]. Moreover, the formation of an interfacial MoSe2 layer is a serious problem for cells. A reverse correlation between the device performance and interfacial MoSe2 thickness has been observed [4]. Moreover, the loss of Sn and Zn during the deposition or annealing process also affects the conversion efficiency of CZTSe solar cells [5]. The third problem is the existence of some intrinsic defects acting as the recombination centers. In our opinion, the magnetron sputtering is a main stream of fabrication method to prepare photovoltaic films. The advantages to sputtering directly from a compound target-low temperature deposition, without toxic source, potential for high deposition rates, good uniformity, high material utilization-make it worth pursuing in the preparation of CZTSe thin films. While, up to now, all CZTSe solar cells with the highest efficiency is given by the C
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