ADVANCED MATERIALS AND FABRICATION METHODS FOR ORGANIC SOLAR CELLS

Abstract

<p>New electrochemical deposition methods have been developed for the fabrication of advanced composite coatings for organic solar cells and hybrid organic solar cells. The methods are based on electrodeposition of conjugated polymers and composites. In this work, poly[3-(3-N,N-diethylaminopropoxy)thiophene] (PDAOT) and poly(9,9-bis(diethylaminopropyl)fluorine- co-phenylene) (PDAFP) were used as electron donors. Single walled carbon nanotubes (SWNTs), ZnO and Ti0₂ were used as electron acceptors. Also co-deposition of PDAOT and PDAFP has been developed in order to broaden the absorption range.</p> <p>An electrophoretic deposition (EPD) method has been developed for the deposition of nanostructured ZnO and Ti0₂ films. The stabilization and charging of the nanoparticles in suspensions was achieved using organic molecules, such as dopamine and alizarin yellow (AY) dye, which were adsorbed on the oxide nanoparticles. The adsorption mechanism is based on the complexation of metal ions at the surfaces of oxide nanoparticles. Cationic dopamine additive was used for the formation of deposits by cathodic EPD. The adsorption of anionic AY on the oxide nanoparticles resulted in charge reversal and enabled the formation of anodic deposits. The method enabled the co-deposition of ZnO and Ti0₂ and the formation of composite films.</p> <p>Electrophoretic deposition (EPD) method has been developed for the fabrication of Ti0₂ films. Benzoic acid and phenolic molecules, such as 4-hydroxybenzoic acid, 3,5-dihydroxybenzoic acid, gallic acid, salicylic acid and salicylic acid sodium salt were investigated as charging additives for the EPD of Ti0₂ particles. The deposition yield has been studied as a function of the additive concentration and deposition time for cathodic deposits obtained from the suspensions, containing benzoic acid, 4-hydroxybenzoic acid, 3,5-dihydroxybenzoic acid and anodic deposits prepared from the suspensions, containing gallic acid and salicylic acid sodium salt. The results obtained for the phenolic molecules with different number of OH groups were analyzed and compared with corresponding experimental data for benzoic acid without OH groups. The adjacent OH groups, as well as adjacent OH and COOH groups bonded to the aromatic ring of the phenolic molecules were beneficial for adsorption of the molecules on oxide particles. The adsorption mechanisms involved the interaction of COOH groups and OH groups of the organic molecules with metal ions on the particle surfaces and complexation.</p> <p>The functional dispersants investigated in this work can be utilized for dispersion and functionalization of the nanoparticles and fabrication of hybrid large area organic solar cells. The new deposition method can be applied for the fabrication of dye-sensitized solar cells.</p>