通过气相沉积法成功地原位合成了膨胀石墨/碳纳米管复合材料,利用扫描电镜、拉曼光谱和X射线衍射仪确定得到碳纳米管插层的膨胀石墨三维多孔复合结构,并通过循环伏安法、交流阻抗法和恒流充放电等对其电化学性能进行测试。结果表明,膨胀石墨/碳纳米管在1 m V/s扫速速率下的比电容达到149.5 F/g,且倍率性能表现出色;同时1 000次充放电后比电容仍保持94%,具有很好的循环寿命,并能保持96%-99%的高充放电效率,功率性能高。
The graphite oxide(GO) was prepared based on the modified Hummers method, then reacted with zinc acetate aqueous, sodium hydroxide aqueous and hydrazine hydrate, and was doped into ZnO eventually to form graphene doped ZnO, an alternative transparent conducting oxide(TCO) for solar cell applications. The samples were characterized by Raman spectrometer, X-ray diffractometer, Fourier transform infrared spectroscopy and scanning electron microscope, and compared with widely used aluminum doped ZnO(AZO) in resistivity and transmissivity. The results show that the transmissivity of graphene doped ZnO reaches the same level as that of AZO in visible light band. In ultraviolet light wave band, the transmissivity of graphene doped ZnO reaches as high as 50%, exceeding that of AZO which is only 20%. The resistivity of optimized graphene doped ZnO is1.03 × 10-5Ω· m, approaching AZO resistivity which is about 10-4—10-6Ω· m. As a result, graphene doped ZnO may have potential applications in the area of TCO due to its low cost and high performance.
Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation （VTE） method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition （CBD）. It is found that the films deposited at a high substrate temperature （200 ℃） have a preferential orientation along （002） which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV-2.56 eV. Culnl_xGaxSe2 （CIGS） solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology.
