Dye Sensitized Solar cells: synthesis and applications of a novel sensitizer and pentacene as hole conductor material

The electricity that is possible to produce by solar energy (photovoltaic technology) using the socalled solar cells, is presently a rapidly growing but nevertheless relatively expensive renewable energy form. Recently however, new molecular photovoltaic materials have been developed, which could enable production of low-cost solar cells in the future. This thesis begins with a discussion of the current status of the PV technology and an introduction to to the fundamentals of organic photovoltaics has been furnished as well. Follow a review on the performance results of organic solar cells categorizing the cells by their device architecture. The dye-sensitized solar cell (DSSC) is an electrochemical solar cell where light absorption occurs by dye molecules attached to a nanostructured TiO2 electrode. An introduction to the DSSC is given including a description of the operating principle of the cell and a discussion of the physical and chemical processes behind it. A systematic literature review is done on the materials and most essential preparation methods of the standard DSSC. The performance of the DSSC is reviewed in terms of the energy conversion efficiency and the long term stability. The glass-based DSSC technology is on the verge of commercialization and the manufacturing cost estimates for the technology are minor to the projected costs of other PV technologies. The important directions of development are the transition from glass substrates to plastic foils and from batch processing to continuous processing as well as the use of a solid state electrolytes or hole conductor layers. It was decided to give an emphasis to the dye-sensitized solar cell technology in the first place. This because on one hand the dye-sensitized solar cell was known as the most actively studied molecular solar cell technology and the one closest to commercialization and on the other hand it was chosen for the subject of the experimental part of the work.Experimental results are reported including a synthesis of a novel synthetic Ruthenium-dye and with this, a preparation and testing of a series of this Ruthenium-dye based DSSCs. The photovoltaic performances were tested with two different electrolytes: tBuNH4+I-/iPrCN 0.4M (Voc=0.47V Isc=1mA FF=61.2% η=0.3%) and Li+ I-/iPrCN 0.4M (Voc=0.33V Isc=2mA FF=61.2% η=0.24%). Moreover has been synthesized a pentacene “spin-coatable” precursor, which was then employed to obtain a pentacene (as hole conductor) based DSSC.The current density vs. voltage in the dark and under illumination (AM1.5) were measured with and without an Al2O3 blocking layer and with different times of exposure to bromine and iodine. Li[CF3SO2]2N and 4-tert-butyl pyridine was added in the solution in an attempt to improve the device performance and stability. By using chlorobenzene as deposition solvent of the pentacene precursor and varying the additives, has been obtained VOC=300mV, ISC= 1mA, η=0.25% as best result