[CCoE Notice] [CCOE Notice] PhD Dissertation Presentation

[Abercrombie, Irene F]

PhD Dissertation Defense
Direct Patterning of Conductive Polymer Domains For Photovoltaic Devices
Suchanun Moungthai
Date: Wednesday, July 18, 2012

Location: Chemical Engineering Conference Room, S234
Time: 1:30 PM

Committee Chair: Dr. G. Stein


In the developed world, the demand for energy is increasing tremendously. Nowadays, the main sources of energy are natural resources like oil and coal, and their supply could run out in the near future. In addition, burning fossil fuel produces large amount of carbon dioxide which is linked to global warming. We need an alternative source of energy that is clean, renewable and sustainable. Photovoltaics is one of the most interesting alternative energy sources for the future energy, as this technology could potentially generate clean, efficient, and reliable electricity. Most products in the marketplace are based on silicon, and these devices require a lot of energy for the fabrication process, driving up their cost and reducing the benefit. Polymer solar cells can be made at a very low cost, and offer additional advantages such as flexible, light weight modules that can be made in a variety of sizes and shapes. A typical polymer solar cell is made from a partially phase-separated polymer/fullerene blend. The main problem for polymer solar cell is their low power-conversion efficiency, which is partly controlled by the active layer morphology.
The objective of this work is to develop a system to study the effects of active layer morphology on device function. The approach developed in this work uses electron-beam patterning of polymer semiconductors to build model polymer/fullerene devices based on electron-beam patterning of polymer semiconductors. Electron-beam patterning generates conductive nanostructures or microstructures through an in-situ cross-linking reaction, where the size, shape, and density of polymer domains are all tunable parameters. Cross-linked polymer structures are thermally-stable and solvent-resistant, so they can be incorporated into devices that require thermal annealing or solution-based processing. This method was validated by building "gradient" and nanostructured poly(3-hexylthiophene)/fullerene solar cells. These model devices exhibit good power-conversion efficiencies, which are explained by a polymer cross-linking mechanism that largely preserves the π-bonds responsible for light absorption, charge generation, and charge transport. The flexible methodology can be used to study the effects of domains size and interfacial area on optoelectronic function.
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