III Generation Photovoltaic: Study, preparation and characterization of materials and devices for Energy

This thesis provides a detailed exploration of dye-sensitized solar cells (DSSCs), focusing on the performance of seven advanced sensitizers optimized for small active area DSSCs (<0.3 cm²). The primary goal is to identify effective sensitizers for practical applications by evaluating parameters like power conversion efficiency (PCE), short-circuit current density (Jsc), fill factor (FF), open-circuit voltage (Voc), and optical properties such as maximum absorption wavelength (λmax) and extinction coefficient (ε). The study highlights the enhancement of DSSC components to optimize light absorption below 650 nm, ensuring stable and reliable performance. Sensitizers—C101, C106, N719, N749, Y123, D35, and D35cpdt—were specifically tailored for small-area DSSCs. Integrating these with materials like FTO-glass, electrolytes, and catalysts yielded PCEs exceeding 6.5%, with refinements achieving values over 10%, making them suitable for bifacial solar cells harvesting light from both sides. Properties such as light absorption, electron injection efficiency, redox potentials, scalability, and environmental stability were investigated, identifying C106, C101, and Y123 as top candidates with PCEs above 7%. N719, N749, D35, and D35cpdt showed moderate efficiency, suitable for cost-sensitive or niche applications. This analysis emphasizes the need for optimizing the DSSC environment, particularly electrolyte compatibility and photon reflection, to achieve peak efficiency. Future research directions focus on enhancing sensitizer-electrolyte synergy and developing novel materials. The study also examines the photoelectrochemical properties of hybrid dyes C106 and Y123 anchored on mesoporous TiO₂ and used as sensitizers in Grätzel solar cells. C106, a ruthenium polypyridine complex, features a red-shifted MLCT band and high ε due to a sulphur atom in its bipyridyl ligand. Y123, a metal-free dye with a triarylamine donor group and CPDT π-bridge, exhibits exceptional light absorption and electron transfer capabilities. Both dyes, optimized for small-area DSSCs, achieved notable results, with a bifaciality factor of 93% for C106 and a PCE of 12.8% for Y123. C106 excelled in electron injection speed and stability, while Y123 benefited from its high extinction coefficient and efficient D–π–A configuration. Bifacial DSSCs leveraging these dyes are promising for building-integrated photovoltaics (BIPV). By excluding scattering layers, optical properties essential for bifacial operation are preserved, enhancing energy harvesting. This study underscores the need to optimize sensitizer-electrolyte interactions and other cell components for maximum efficiency. Additionally, the research addresses upscaling DSSCs from small (<1 cm²) to larger areas (≥1 cm²), tackling efficiency and stability challenges. Using C106 and Y123, performance was evaluated under various conditions, including bifacial configurations. Significant efficiency losses were noted with scaling due to resistive losses in the TiO₂ photoanode and TCOs. Optimization strategies included controlled TiO₂ strip dimensions and enhanced TCO conductivity, achieving a PCE of 8.36% with Y123-based DSSCs after 96 hours of stability testing. The bifacial configuration showed PCE improvements from the albedo effect, reaching 8.09% (front) and 6.27% (back) for Y123-based devices. Advanced modeling revealed an exponential relationship between efficiency and active area, emphasizing optimization of absorption coefficients, injection efficiency, and charge collection efficiency. Novel architectures leveraging 3D transport pathways and surface passivation were explored to mitigate recombination losses. Finally, the potential application of DSSCs as photodiodes for hemoglobin (Hb) quantification was investigated. This study, conducted in collaboration with Ontario Tech Institute, explored DSSCs as cost-effective biosensors for Hb analysis from pin-prick blood samples. Challenges like electrolyte stability were addressed, and a calibration curve for Hb concentration based on current response was developed. This research demonstrates the feasibility of DSSCs in biomedical diagnostics, highlighting their sensitivity and specificity for low-resource settings.