Year: 2015
Type: dissertation
Abstract: The global challenge of sustainable development, clean energy and climate change needs to be pursued by development of energy technologies. Moreover the energy sector is responsible of two thirds of the world’s greenhouse-gas (GHG) emissions ; therefore the world needs to change the inefficient energy system based on fossil fuels to renewable sources as sunlight, wind, rain, waves, tides, biomass and geothermal heat. Besides solar energy is available throughout the world as radiant light or heat from the sun, using technology such as photovoltaics devices. New generation of photovoltaics can provide an alternative and complementary approach for the exploitation of solar energy; offers low manufacture cost, they are flexible, light, and more environmental friendly; the most promising for their remarkable progress are: organic solar cells, hybrid dye sensitized solar cells, and perovskite solar cells. Nevertheless, in this thesis the first two types of cells will be widely described focusing on devices comprising porphyrins, these molecules have been explored due to their robustness, thermal stability, rich metal coordination chemistry, strong aromaticity, optical, electronic and magnetic properties. \n \nContent \nIn the first chapter twelve novel small molecule porphyrins, with configuration A-?-D-?-A, were synthesized and characterized to be applied in solution processed bulk heterojunction solar cells (BHJSC). Also zinc porphyrin core (D) and ? conjugated linker were separated by an ethynyl group, to improve the planarity and enhance the ? conjugation of the system. Moreover each molecule comprise two strong ? electron withdrawing moieties (A) to control the absorption spectrum in the near infrared region, by a conjugation with electron rich aromatic units. In order to study, all molecules were synthesized and properly characterized, photophysical and electrochemical properties were measured, and theoretical HOMO-LUMO orbitals and optimized geometries were calculated. Additionally, to complete these studies, devices performance was evaluated and the best PCE (4.24%) was achieved with PC71BM:SA4 (4:1 w/w) (comprising a mesityl zinc porphyrin core, (E)-1,2-bis(3,4-dihexylthiophen-2-yl)ethylne as ? conjugated linker and 3-ethylrhodanine as acceptor), with a high short circuit current (JSC) of 13.2 mAcm-2. \nIn the second chapter six novel dyes bearing triphenylamine donor groups were synthesized and characterized. The absorption and electrochemical properties were investigated to determine the electronic features of these compounds. Moreover these molecules were employed as sensitizer for Dye Sensitized Solar Cells (DSSCs), and their efficiencies were measured in nanocrystalline TiO2. The best PCE (6%) was achieved for SA12 employing two thiophene rings connected by a double bond as spacers between the conjugated porphyrin core and the anchoring cyanoacrylate group. \nNovel designs of porphyrin and improvements in photovoltaic devices can be achieved. Therefore, there is still much work to be done to improve solar cells. Moreover, in the last years the research on this thematic is allowing to develop best photovoltaics.
Authors: Arrechea Alvarado, Marlene Susana
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2286199149