Phys Rev B 1972, 6:4370–4379.CrossRef 23. Marinica DC, Kazansky AK, Nordlander P, Aizpurua J, Borisov AG: Quantum plasmonic: nonlinear effects in the field enhancement of a plasmonic nanoparticle dimer. Nano Lett 2012, 12:1333–1339.CrossRef 24. De Abajo FJ G: Nonlocal effects in the plasmons of strongly interacting nanoparticles, dimers, and waveguides. J Phys Chem C 2008, 112:17983–17987.CrossRef 25. Oulton RF, Bartal G, Pile DFP, Zhang X: Confinement and propagation characteristics of subwavelength plasmonic modes. New J Phys 2008, 10:1367–2630.CrossRef Competing interests The authors declare that they have no competing

interests. Authors’ contributions WW proposed the asymmetric idea, calculated properties of the proposed waveguide, and wrote the manuscript. XZ, YH, and XR analyzed the data and revised the manuscript. All authors read and Volasertib manufacturer approved the final manuscript.”
“Background Cu2ZnSn(S,Se)4 (CZTSSe) quaternary semiconductors attract a lot of interest for thin-film solar cells [1]. Competition in the solar cell market is nowadays hard-hitting,

so it is getting more concern on the cost in the manufacturing of the thin-film solar cells. CZTSSe consists Selleck GSK621 of relatively cheap and earth-abundant elements of Zn and Sn. In contrast, Cu(In,Ga)Se2 (CIGS), which is now mostly promising for commercialization, has expensive and rare elements of In and Ga. CZTSSe shows high absorption coefficient and the band gap of it can be tuned with changing S and Se composition. So far, the highest conversion efficiency

of CZTSSe is reported as 11.1% in non-vacuum process with hydrazine [2] and 9.2% in vacuum process by co-evaporation [3, 4]. Very recently, Solar Frontier announced the conversion efficiency of 10.8% in the CZTSSe solar cell module Depsipeptide chemical structure of 14 cm2[5], which Selleck BAY 11-7082 indicates presumably 12 to 13% of the conversion efficiency in the cell level. For large area deposition, sputtering methods have an advantage in production of CZTS-based solar cells [6, 7]. It is likely that compound sources such as ZnS and SnS can improve adhesion between the substrate and the thin film during deposition. Moreover, it is believed that the method can increase grain size, control composition, and improve surface morphology of precursors [8, 9]. In order to put Se into the as-grown CZTS stacked precursors, optimization of annealing conditions of the precursors in Se atmosphere is decisively important. In previous reports, the different stacking orders of precursors determine the crystallinity and grain growth of the CZTSSe thin films [10, 11]. The results showed dense morphology and little voids on surface in case of Cu/SnS/ZnS/Mo/glass [12, 13]. There are some models to exhibit the advantageous properties of grain boundaries (GBs) of polycrystalline CIGS. Jiang et al. proposed that GBs acting as a factor to improve cell performance contrary to single-crystal solar cells by scanning probe characterization.