Research And Application Of Graphene-based Composites In CdS Quantum Dot Sensitized Solar Cells

The global energy crisis has prompted the development of quantum dot sensitized solar cells(QDSSCs).At present,optimizing the device structure of QDSSCs and improving its photovoltaic performance has become a research hotspot for scholars all over the world.People have tried to use graphene-based composite as photoanode or counter electrode materials for solar cells and explored its effect on the photovoltaic performance of QDSSCs since the excellent optical,electrical and mechanical properties of graphene are highly consistent with the materials required for solar cells..In this paper,CdS quantum dots(QDs)was used as photosensitizer to improve the photovoltaic performance of QDSSCs;considered the graphene-based composite as main line;incorporated the graphene into nanostructured TiO2 and NiS as photoanode and counter electrode materials respectively for CdS QDSSCs and explored the cells performance after the incorporation of graphene.The X-ray diffractometer(XRD),field emission scanning electron microscope(SEM),energy spectrum quantitative analyzer(EDS),high power transmission electron microscope(HRTEM),Fourier infrared spectrometer(FTIR),Raman spectrometer(Raman),UV-visible spectrophotometer(UV-vis),ECS electrochemical workstation and volt-ampere characteristic curve(J-V)test equipments were used for structural and photovoltaic performance analysis of prepared samples during the experiment.The relevant research contents and conclusions of this paper are as follows:(1)A uniform and orderly rutile TiO2 nano-array(NRs)was grown on the surface of fluorine-doped SnO2(FTO)conductive glass by one-step hydrothermal method.Different proportions of graphene oxide(GO,prepared by modified Hummers method)and anatase phase TiO2 particles were ultrasonically oscillated evenly and then compounded them with TiO2 NRs.After thermal reduction,the graphene(rGO)/anatase-rutile TiO2 photoanode was obtained and assembled into a solar cell with Cu2S as counter electrode.It was found that the photoelectric conversion efficiency of the solar cell composed of anatase-rutile TiO2 photoanode(labeled as TGrO)was 1.77 times that of pure rutile phase TiO2 NRs.When the ratio of GO/anatase TiO2 complexed with rutile phase TiO2 NRs was 5%,the corresponding photoanode(labeled as TGr5)achieved the highest photoelectric conversion efficiency of 1.26%,which was 2.93 times and 1.66 times that of pure TiO2 NRs and TGrO photoanode,respectively.The photoelectric conversion efficiency of the solar cell assembled by TGr5 photoanode and used the Pt as counter electrode was 0.88%,which was 30.16%lower than that of Cu2S.(2)CdS QDs were loaded onto the surface of the TGr5 photoanode by continuous ion layer adsorption(SILAR).When the cycle sensitization period of CdS QDs was 10,the CdS QDSSC assembled with the Cu2S counter electrode achieved a maximum photoelectric conversion efficiency of 2.20%,which was 1.75 times that of the unsensitized TGr5 photoanode.The TiO2 NRs and the anatase-rutile phase TiO2 photoanodes doped with different rGO contents were respectively sensitized with CdS QDs for 10 cycles and assembled into solar cells.The testing results showed that the photoelectric conversion efficiency of CdS QDSSCs assembled by TGr5 photoanode was still the highest,which was 2.78 times and 1.50 times of TiO2 NRs(0.79%)and TGrO(1.47%),respectively.The photoelectric conversion efficiency obtained by using the Pt as the counter electrode was 1.32%,which was 40.00%lower than that of the Cu2S.(3)Pure NiS nanoparticles and rGO/NiS composite with different rGO contents were prepared by hydrothermal reaction method.The obtained samples were prepared as counter electrodes and the TGr5 which sensitized by CdS QDs for 10 cycles was used as photoanode and assembled them into solar cells.The experimental results showed that when the concentration of GO solution in the hydrothermal reaction was 1 mg/mL,the prepared solar cell assembled by the rGO/NiS composite as counter electrode reached the highest photoelectric conversion efficiency of 2.47%,which was 1.87,1.12 and 1.22 times of Pt(1.32%),CuS(2.20%)and pure NiS counter electrode(2.03%),respectively.