الفهرس 
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Abstract
In this current study different ZnO nanoparticle )ZnO NPs) were successively synthesized by four different wet chemical techniques (Simple precipitation, Reflux, Sol Gel, and Combustion techniques) using zinc acetate dihydrate Zn(CH3COO)2.2H2O and methanol as a row materials. Simple precipitation technique: Three groups of ZnO NPs have been synthesized by simple precipitation technique. In the first group the temperature of the ZnO NPs colloidal was heated at 60 oC, pH = 12, and time of heating was varying from 15 min to 90 min. The best sample was when the time of heating about 60 min. In the second group the temperature of the ZnO colloidal was fixed at 60 oC, time of heating was about 60 minutes and pH value was varying from 8 to 14. It was found that the best sample was when the pH value about 14. In the third group the ZnO colloidal prepared in group two where, the temperature of the ZnO colloidal was at 60 oC, pH = 14, and time of heating was 60 min. then the ZnO colloidal transferred into 100 ml Teflon line stainless steel hydrothermal autoclave reactor. The colloidal heated at 160 oC for different times up to 10 hours. It was found that the best sample when the time of heating using autoclave about 3 hours.
Reflux technique: is a green technique with very simple and low price. No additives such as acidic or basic solution is required. Pure and cupper doped )ZnO NPs), (ZnO:Cu), with compositional formula CuxZn1-xO (x=0,1,2 and 5 molar ratio). Cu(CH3COO)2 was used as the cupper source.
Sol Gel technique: Oxalic acid solution acted as precipitation agent, It’s found that, 400 Co is the minimum temperature requires to ensure that all organic species were expelled from the products to produce pure ZnO NPs.
Combustion technique: It is very simple, low cost, fast technique which give us large amount of pure metal oxide. Zinc acetate dihydrate Zn(CH3COO)2.2H2O and different amounts of urea CO(NH2)2 are dissolved in triple distilled water. The solution was heated in ambient atmosphere using muffle furnace at 500Co. The ratio between fuel CO(NH2)2 and Zn(CH3COO)2.2H2O is improved in order to select the a appropriate ration. In general, electron dispersive x-ray analysis (EDX) spectra illustrated that the product is pure ZnO and that only two elements, Zn and O are exist in the products. XRD studies patterns indicated that the ZnO NPs have been grown with hexagonal phase, wurtzite structure with lattice parameters about a=0.3242 nm and c=0.592 nm. No other phases have been observed, which further confirmed the formation of pure ZnO NPs with single phase and the size of the synthesized ZnO NPs ranged between(17.4nm to 40 nm). The results of HRTEM micrograph characterizations image, it is clearly observed that the average particle size (D) was consistent with the calculation results from XRD.
HRTEM micrograph showed that ZnO NPs is nearly spherical in shape. The results showed that, increasing of heat or time of heating is leads to increases of the NPs size as well as decreases of the energy gape. Also the size of NPs increases as pH value increase because the number of (OH-) ions increases.
We are able to fit the PL spectra with four peaks. The first peak appeared near band edge (NBE) near 360 nm. The second peak appeared near 431nm (blue), the third peaks appeared near at 441 nm and the fourth peak appeared near at 650 nm.
Dye sensitized solar cells (DSSCs) is a third generation solar cell. It is a promising as alternative for the silicon solar cell. ZnO layer was deposited using doctor blading. The resulting film were preheated at 100 oC for 15 min., then calcination temperature at 450 oC for 40 min. to remove any organic remainder. DSSC consists of fluorine doped tin oxide (FTO) coated dyed ZnO layer as front electrode (photo electrode). Platinum (Pt) deposited into FTO glass which acts as a back electrode (counter electrode). Electrolyte injected between two electrodes to regenerate losses of electrons.
The UV-VIS absorption of different dyes Eosin B(EB), Eosin Y (EY) and Rhodamine B (RB) measurements have been performed using double beam Shimadzu UV-1601 PC. Photovoltaic measurements were carried out using J-V measurements.
Combustion technique was the best technique to produce high purity ZnO NPs as well as higher performance DSSC and the results illustrated that EY corresponds to the highest efficiency. The best performance for all DSSCs prepared by different techniques was the DSSC which used U4 ZnO NPS as a semiconductor layer and EY as a photo sensitizing dye. Full photovoltaic parameters of the best cell are Jsc = 4.829 mA.cm-2, Voc = 0.516 V, Jm = 3.962 mA.cm-2, Vm = 0.318V, Pm = 1.26V, FF = 50.57 % and η =1.26 %. The best efficiency may be attributed to slower decay of Voc and lower recombination constant as well as it has a good uploading.