Synthesis and characterization of mangosteen (Garcinia mangostana) Dye-sensitizer on a Polypyrrole (PPy)/Nano-titanium Dioxide (TiO2) composite via horizontal vapor phase crystal growth technique for solar application

• Main Author: Advincula, Al Otayde
• Format: text
• Language: English
• Published: Animo Repository 2015
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/4813
• Institution: De La Salle University

Horizontal Vapor Phase Crystal Growth Technique (HVPCGT) was employed in the synthesis of nano-TiO2 on the photoelectrode of natural-based dye-synthesized solar cells (DSSCs). Anatase and rutile TiO2 powder were used as bulk material having dimensions of 70-600 µm and 50-200 µm, respectively. Anatase-to-rutile TiO2 ratios of 60%:40% (3:2), 75%:25% (3:1), 90%:10% (9:1) were prepared through sonication, filtration and drying under 50 Å°C for an hour. Mixed powders were loaded to the sealed-end and glass substrates were positioned 140 mm from the loaded area. The tubes were set to have 10-6 Torr pressure then the loaded region up to the half of the tubes were subjected to growth temperature of 1200 Å°C with an increment of 100 Å°C and dwelling time of 6 hours. XRD patterns bulk materials showed strong intensity peaks at d = 3.51 Å… (101), 2.36 Å… (200), and 1.89 Å… (004) for anatase TiO2 and at d = 3.23 Å… (110), 2.48 Å… (111), and 1.68 Å… (101) for rutile TiO2. SEM micrographs showed deposition of monodispersed and isolated agglomerations, cubes, rods, wires, spheres, flake-like, micro- and nano-dimensions of TiO2 of diverse orientations. PPy thin films were synthesized with varying thickness of 7.45 µm 0.50 µm, 15.3 µm 0.47 µm, and 32.1 µm 0.55 µm, using synthesis times of 80 min, 90 min, and 100 min, respectively. Conductivities were found to be 260 S/cm, 164 S/cm, and 86.5 S/cm where this property was observed to increase as thickness increases. Mangosteen dye as natural dye photosensitizer showed strong absorption in UV and visible light spectrum with the highest peak located at 601 nm. The optical bandgap was computed to be 1.97 eV while cyclic voltammetry showed electrochemical bandgap of 2.09eV while FTIR spectroscopy proves the presence of OH and =O. Multilayer nano-graphene powder was deposited on the counterelectrode via sonication-assisted method resulting to flake-like surface with thickness 7.673 µm. In the absence of PPy thin film 3:1DSSC showed the highest solar-to-electric conversion efficiency among natural dye-based DSSCs. The incorporation of PPy thin film significantly enhanced the Voc and Jsc resulting to 0.031 % efficiency. A modified mechanism of nano-TiO2/Dye/Electrolyte/PPy/nano-Graphene DSSC was also presented in this study.