Direct Patterning Of Conductive Polymer Domains For Photovoltaic Devices
Moungthai, Suchanun 1983-
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In the developed world, the demand for energy is increasing tremendously. In this day and age, 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 amounts of carbon dioxide which are linked to global warming. We need an alternative source of energy that is clean, renewable and sustainable. Photovoltaics are one of the most interesting alternative energy sources for future energy, as this technology could potentially generate clean, e cient, 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 bene t. Polymer solar cells can be made at a very low cost, and o er additional advantages such as exible, 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 powerconversion e ciency, which is partly controlled by active layer morphology. The objective of this work is to develop a system to study the e ects 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. 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 e ciencies, which are explained by a polymer cross-linking mechanism that largely preserves the -bonds responsible for light absorption, charge generation, and charge transport. The exible methodology can be used to study the e ects of domains size and interfacial area on optoelectronic function.