الفهرس 
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Abstract
Renewable environment friendly energy resources are needed to meet our clean energy demand. Solar energy is the most prevalent renewable resource on the planet, and efficient conversion of solar energy to more useful forms such as electricity will help meet the increasing demands for energy in the near future. Graphene is one-atom-thick planar sheets of sp2 bonded carbon atoms that are densely packed in a honeycomb crystal lattice ideally suited for implementation in electrochemical and photoelectric applications owing to their remarkable high electron mobility (15,000 cm2/ VS), extremely large surface area (~2600 m2/g), transparency, unique heterogeneous electron transfer and charge carrier rates, widely applicable electro-catalytic activity, and low production costs. Consequently graphene has been utilized beneficially as a promising alternate electrode material in many applications for enhancing specific technological fields and particularly the issues surrounding energy storage and generation. Another promising nonmaterial for energy conversion is Semiconductor whose excitons (electron-hole pair) are confined in all three spatial dimensions. So, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules whose electronic characteristics are closely related to the size and shape. Generally, the smaller the size of the crystal, the larger the band gap leading to several applications in transistors, LEDs, solar cells, and diode lasers. Assembly of semiconductor nanoparticles, on matrices has been studied for their promising optoelectronic applications to enhance the photocurrent generated by these semiconductor-matrices systems, such as CNTs one of the exciting trends in CNT hybrid materials was the assembly of semiconductor nanoparticles onto CNTs. The combination of the two classes of material enables the new hybrid materials to present new properties for potential applications. In comparison with CNTs, graphene possesses similar physical and chemical properties but a better conductivity, larger surface areas, and a higher surface-to-volume ratio, as an unrolled CNT. Furthermore, graphene can be easily prepared from graphite through chemical oxidation–reduction reactions, and the potential low manufacturing cost makes it a promising candidate as an alternative to CNTs for catalyst support and nanoelectronic devices. In this thesis, the synthesis of Graphene by modified Hummer method to obtain Graphene Oxide followed by chemical reduction to obtain Graphene, CdSe quantum dots synthesized using hot injection method, Graphene CdSe nanocomposite synthesized by the same previous method with addition of Graphene to the mixture and Zinc Oxide nanocones synthesized by Microwave irradiation method, all the previous materials was characterized and verified. I study the effect of Graphene on the CdSe quantum dots rate of particle growth as full width at half maximum (FWHM) decrease with respect to the CdSe QDs alone this mean that; the graphene sheets enhances the particle growth and the formed particles have small size distribution, optical properties of QDs effected strongly which could be noticed from quenching of QDs emission due to Graphene presence as it receive electrons from QDs facilitating the charge separation and reduce the recombination, also increase in stock shift of Graphene CdSe nanocomposite means that QDs are well adsorbed on the Graphene sheet. The effect of surface modification for CdSe QDs and Graphene CdSe nanocomposite by replacing the long chain capping agent (TOP- O.Am.) by pyridine were operated and confirmed with FT-IR results and TEM images. Also, I study the photoelectric properties of these materials before and after surface modification showing that the surface modified graphene CdSe QDs has the best short circuit current (ISC) and open circuit voltage (VOC) readings.