Shufang Wang,Shanshan Chen,Guoying Yan,Fuqiang Liu,Shouyu Dai,Jianglong Wang,Wei Yu,Guangsheng Fu
c-axis oriented nanocrystalline Bi 2 Sr 2 Co 2 O y thin films with the average grain size of 25 nm have been achieved by chemical solution deposition combined with a rapid annealing process in oxygen. The resistivity and Seebeck coefficient of the nanostructured films are about 7.0 mΩ·cm and 171 μV/K at 873 K, resulting in a power factor 2–3 times larger than that of the best reported value in the coarse-grained Bi 2 Sr 2 Co 2 O y polycrystalline bulks. Since the thermal conductivity can be greatly reduced due to the increased phonon scattering at the grain boundaries of nanocrystalline films as well as at film surface and at film/substrate interface, great improvements in the ZT are expected in the nanocrystalline Bi 2 Sr 2 Co 2 O y thin films .
Yanchun Yang,Xiaojiao Kang,Lijian Huang,Song Wei,Daocheng Pan
Earth abundant Cu 2 ZnSn(S,Se) 4 (CZTSSe) has been considered as one of the most promising thin film solar cell absorber candidates. Here, we develop a facile water-based precursor solution approach for depositing high-efficiency Cu 2 ZnSn(S,Se) 4 thin film solar cells. In this environmentally friendly approach, inexpensive elemental Cu, Zn, Sn and S powders are used as the starting materials and are dissolved in the aqueous solution of thioglycolic acid and methylamine, forming a homogeneous precursor solution for depositing Cu 2 ZnSnS 4 nanocrystal thin film . As-deposited CZTS nanocrystal thin films are selenized to form the large-grain CZTSSe absorber layers . It was found that Na doping plays an important role in the formation of the extremely dense and flat CZTSSe absorber layer, and fill factor can be significantly improved for Na-doped CZTSSe solar cells, which lead to a photoelectric conversion efficiency of 6.96% with an open-circuit voltage of 378 mV, a short current density of 28.17 mA cm −2 , and a fill factor of 65.4%.
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