Synthesis And Photovoltaic Properties Of Small Molecules Based On Porphyrin Through Side Chain Modification

Organic photovoltaics(OPVs) are considered a promising solar energy conversion technology having the advantages of being solution processable, light weight, low cost and flexible.Photosynthetic pigments related to the chlorophylls, such as porphyrins, are particularly good candidates for optical and optoelectronic applications, due to their large molar absorption coefficients, tunable electro-chemical and photophysical properties via central metal insertion and/or introduction of various substituents at the macrocycle peripheral positions.Peng and co-workers, by employing a porphyrin with two diketopyrrolopyrrole units and ethynyl bridges at meso positions, along with PC60 BM as the electron acceptor, reported a BHJ organic solar cell with a PCE value of 3.71%, which was significantly improved to 4.78% when the BHJ active layer was processed with pyridine.Recently, Peng et al. employed a porphyrin molecule with less bulky substituents at the periphery as donor material along with PC61 BM as the acceptor for solution processed organic solar cells and achieved a PCE up to 7.23%.Compared to continue to design and synthesis of new conjugated system, appropriate adjustment flexible side chains to improve the performance of organic semiconductor device is an effective method. The paper work is in A-π-D-π-A structure based on porphyrins and DPP constituted by side chain modifications, to ensure the level of small changes to further improve the solubility of the premise of small molecules, film carrier mobility and other properties, so as to enhance optical and electrical properties.In the second chapter, under A-π-D-π-A structure based on porphyrins and DPP, we designed and synthesized three small molecules by side chain modifications on porphyrin. By improving the solubility of the molecule, the steric configuration and intermolecular interactions, thus affecting the absorption of sunlight, the energy level and the carrier transport properties, thereby improving the properties of the blend morphology and photovoltaic devices. Among them, the BHJ OSCs fabricated by solution spin-coating with Por-PEG-DPP-EH as the donor and PC61 BM as the acceptorshowed a PCE of 6.23%. This shows that having a hydrophilic side chain has a positive effect on solubility, film-forming properties and improve the photovoltaic performance of the molecule.In the third chapter,in order to have a deep and comprehensive understanding of the impact of this special performance of PEG chains of porphyrin-DPP system, we designed and synthesized two other small molecules Por-OC8-DPP-PEG and Por-PEG-DPP-PEG through replacing the position and number of PEG chains.Then systematically investigation was conducted on their optical,electrical,hole mobility and photovoltaic properties.In this thesis, we designed and synthesized Meso-tetra-substituted porphyrin small molecules based on several acceptors for application in solution-processed BHJ photovoltaic cells and organic field-effect transistors. The π-conjugation of the whole molecule are expanded, the optical bandgaps and energy levels are tuned, and the charge mobilities are enhanced by introducing electron-withdrawing units and acetylene bonds between the zinc porphyrin unit and electron-withdrawing units. Thus, they exhibited superior photovoltaic performance based on these molecules devices...