This report will focus on the initial stage, in which FTO glasses will be used as counter electrodes (CEs) and help to form the sensor completely. After the optimal hybrid structure of sensitizer can be formed on the surface of BPs, FTO glasses will be removed and a novel structure of DSC will be proposed in the future to achieve excellent conductivity with highly flexibility. 9.2 Materials and Methods Experimental Methods. The fabrication methods of distributed sensors will be partially adapted from the methods of wire-shaped sensors [20, 21]. When light hits the dye particles and other additives, electrons will be generated which will be further transmitted to BPs and FTO glasses via the hybrid sensitizer (QDs and TiO2). The cycle will be completed when electrons finish their journey through the load and reach the other Pt coated FTO glass (CE). Coating method used here is known as Doctor Blade Technique (DBT). Instead of scotch tape, Teflon sheet will be cut as coating screen (3 3 cm) (Fig. 9.2), which has high temperature resistance. Figure 9.2 shows the fabrication procedure for BP-based distributed sensor in detail, and the thickness of Teflon mode decides the thickness of TiO2 coating. A basalcoating solution used titanium isopropoxide (TiP) as a precursor, which was applied before major sol-gel method and worked as a foundation for the main-coating [17, 36]. The preparation of major sol can be summarized as follows: Nanowater and 70 wt% HNO3 were mixed together as solution A. Solution B consisted of Nano-Water, Acetic Acid Glacia, Triethylamine and TiP in same amount, Acetic Acid Glacia, Triethylamine and TiP. Solution A and B were prepared individually and mixed together after fully stirring. The mixture was heated in an autoclave at 240 C, and 50 vol% of the solvent of resultant solution were evaporated at 75 C. Polyethylene glycol was then added into the sol before coating. This sol was applied on the BPs (WEs) via DBT, and then BPs went through a heating process at 350 C. This DBT-heating process was repeated several times to reach the height of Teflon screen (~20 μm). To fill the porous TiO2 structure with as many as QDs, CdS and CdSe QDs were coated with chemical bath deposition (CBD) method. WEs were dipped into a 0.5 M Cd(NO3)2 ethanol solution, rinsed with ethanol and dried in the room temperature (RT). This step should be repeated twice before WEs are dipped into a 0.5 M Na2S methanol solution and rinsed again with methanol. This whole cycle needed to be repeated twice for a mature coating. The preparation of CdSe QDs was similar except Na2SeSO3 solution needs refluxing at 70 C for a longer time and a higher temperature was required during the dipping process. These treated electrodes were then sensitized overnight by immersing into N719 (N719 ¼[tetrabutylammonium] 2 [Ru (4-carboxylic acid-40-carboxy-late-2, 20-bipyridyl) 2(NCS)2]) dye (0.05 M N719 in the mixture of tert-Butanol and acetonitrile (volume ratio ¼1:1)). The CEs were platinized using sputtering target at 1.5 KV and 5 mA for 60 s before twisting with WEs and finally were soaked in heated electrolyte. Solid electrolyte contained 0.5 M LiI, 0.05 I2 and 0.5 tert-butyl pyridine in 3-methoxy propionitrile (3-MePRN). Poly(vinylidene fluoride-co-hexafluoropropene) (5 wt%) was added to confirm the solid state of the electrolyte media. All chemicals used in this experiment were purchased from Sigma-Aldrich. Two kinds of BPs (random and aligned) will be used in trials for comparison. Fig. 9.2 Fabrication procedure for BP-based distributed sensor 9 Buckypaper-Cored Novel Photovoltaic Sensors for In-Situ Structural Health Monitoring of Composite Materials. . . 75
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