Electrochemical Surface Modification for Application in Organic Optoelectronics
Date Issued
2013
Date
2013
Author(s)
Wei, Hung-Yu
Abstract
In this dissertation, we use electrochemical process to modify the surface of conventional organic optoelectronics. To improve the performance of unmodified organic photovoltaics and achieving dual-color electrochromic films.
In the first part (in Chapter 3), we deposited the thiophene monomer on the surface of poly(3,4-ethylenedioxythiophene) (PEDOT) hole transfer layer through electrochemical polymerization process to form a buffer layer connecting the electron donor domain in the active layer and the hole transfer layer. It increased the charge carrier collection efficiency and reduced the recombination due to the contact of acceptor domain with hole transfer layer. Thus, the cell performance was improved. We also proved that we can tune the work function of the polythiophene buffer layer by applying potential, further improve the open circuit voltage of the solar cell device.
In the second part (in Chapter 4), we created a template by spreading polystyrene beads on the ITO substrate. Then grew the PEDOT hole transfer layer bottom-up between the gap of polystyrene beads. After removal of the polystyrene template with solvent, we obtain a PEDOT hole transfer layer featuring bowl-like structure. After depositing the copper phthalocyanine (as the electron donor) and fullerene (C60 or C70 as the electron acceptor) along the feature of the structured PEDOT, we created a bilayer solar cell with structured active layer. Which dramatically increases the donor—acceptor interfaces. Compare with the result of solar cell devices without structure (planar active layer), the structured active layer improves the short circuit current from 4.82 mA cm-2 to 9.18 mA/cm-2; improves the power conversion efficiency from 0.97% to 2.45%.
The third part (in Chapter 5), we used the bowl-like structured PEDOT layer as the bottom layer of electrochromic film and electrochemically polymerize the aniline monomer on the rim of the bowl-like structure. As we apply the potential on the structured PEDOT, the aniline monomer will condense on the sharp edge of the rim, but not the smooth bottom of the bowl-like structure, because of the charge concentration effect, forming a PANI-PEDOT composite electrochromic film. By applying an oxidative potential to this structured composite film, PANI and PEDOT change color simultaneously and the color turns green; while applying a reductive potential to this structured composite film, PANI and PEDOT change color simultaneously and turn blue. The hole structure allows both the bottom PEDOT layer and the top PANI layer to have good contact with the electrolyte, thus providing much higher coloration efficiency than the planar composite film. Also the switching time of the structured electrochromic film became shorter due to the easier contact of electrolyte with both electrochromic materials.
Subjects
有機太陽能電池
共軛高分子
電化學聚合
奈米結構
主動層
緩衝層
SDGs
Type
thesis
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