Electro-synthesis And Photoelectric Properties Of The Graphene/Silver (Selenium) Nanocomposites

Solar cell is a research hotspot in material and energy fields, since it can transform sunlight to power. The solar cells made up of nanonanocomposites have attracted a great deal of academic and industrial interest because of their low cost, easy processing and excellent properties. For nanonanocomposites, however, the photoelectric conversion efficiency and stability need to be improved. It has been found that the structure of active layer and the interfacial contact model play critical role in the performance of solar cells. This master thesis improved the photoelectric conversion efficiency and stability by optimizing the morphology and structure of nanonanocomposites, and the satisfied results were obtained.1. Electrochemical synthesis and photoelectrochemical properties of RGO/AgNDs nanonanocompositeAs known, the surface plasmon resonance (SPR) effect of the AgND can enhance its absorption in visible light region. Here, the nanonanocomposite made up of AgNDs (Ag nanodendrites) and RGO (reduced graphene oxide) was prepared by one-step electrodeposition approach. The RGO/AgNDs nanonanocomposite as-prepared was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffractometer (XRD), ultraviolet visible spectrophotometer (UV) and the Nyquist plots of electrochemical impedance spectroscopy (EIS). The results show that the three dimensional (3D) AgNDs with cubic phase were enwrapped by the thin RGO sheets. The electrodeposition condition and the photoelectrochemical response mechanism was discussed. The RGO/AgNDs nanonanocomposite obtained in optimum condition has high photoelectrical conversion efficiency and long-term stability. Furthermore, the RGO/AgNDs nanonanocomposite exhibited superior electrocatalytic activity toward the reduction of hydro gen peroxide (H2O2), with a wide linear response range of 2.65 mM to 0.08 mM (R2=0.995).2. Electrosynthesis and Photoelectric Conversion of MoS2/AgNDs nanocompositeWe prepared a novel MoS2/AgNDs nanocomposite via a one-step electrodeposition approach, in order to improve the photoelectrical conversion efficiency. The characterization results show that three dimensional (3D) AgNDs with cubic phase are enwrapped by MoS2 nanosheets in the nanocomposite. The photoelectrical conversion mechanism, formation mechanism and effect factors for MoS2/AgNDs nanocomposite were discussed. The test results show that the the plasmon-excited hot electrons were injected from the AgNDs into the MoS2 conduction band of the semiconductors, and in turn the AgNDs acted as a "pool" to gather photoexcited electrons of the MoS2 nanosheets, which suppressed the invalid recombination of the photoexcited electrons with hole pairs. So the MoS2/AgNDs nanocomposite exhibited excellent photoelectrical conversion under visible light.3. Electrosynthesis and Photoelectric Conversion of Selenium Nanowires Wrapped with Graphene Quantum DotsWe present a novel electroreduction method for synthesizing selenium nanowires (NWs) wrapped with reduced graphene quantum dots (rGQDs). In synthesis, the GQDs and H2SeO3 were used as precursors, and cetyltrimethylammonium bromide-(CTAB) micelles were used as so ft-temp late. The structure of the rGQDs/SeNWs nanocomposite as-synthesized was studied by a series of characterization techniques (SEM, TEM, XRD and EIS). Interestingly, compared with pure rGQDs and Se NWs, the rGQDs/SeNWs nanocomposite showed an enhanced photoelectric response to illumination, which originated from the synergistic action of electron-deficient rGQDs and electron-rich Se NWs.