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Molecular Engineering on Semiconducting Polymers for Enhancing Solar Cell Performance

  • Author(s): Chang, Wei-Hsuan
  • Advisor(s): Yang, Yang
  • et al.
Abstract

A promising solution to address the present-day energy crisis is photovoltaic technology. Currently, the market is dominated by inorganic-based materials such as silicon, III-V semiconductors, CIGS, etc. Despite their technical maturity, the energy generated from these devices is still low. This is partially due to the high production cost of these materials. Therefore, the search for next generation photovoltaic technologies that utilize earth-abundant elements with low-cost production processes has been an intensive research area.

Using solution-processable organic polymer semiconductors, polymer solar cells provide an opportunity to efficiently generate energy from sunlight at a reasonable cost. This is due to the ease of synthesis/modification of organic molecules and polymers compared to that of inorganic materials, the easily scalable solution-based fabrication process, and the use of cost-effective, environmentally friendly carbon-based elements. Owing to the vast research efforts over the past decade, the power conversion efficiencies of single- and multi-junction polymer solar cells have recently surpassed the 10% milestone.

During this progression, materials development, driven by the desire to overcome the constraint of P3HT, has played a very important role in advancing the technology. To date, hundreds of photovoltaic polymers have been made through different combinations of conjugated building blocks and suitable functional groups. As a result, several state-of-the-art polymers, such as PTB7, PDPP3T, PBDTDPP and PffBT4T, have shown impressive performance. In order to keep this momentum going, further improvements and deeper insights into materials’ property are certainly needed. In this dissertation, we particularly focus on improving the properties of several state-of-the-art photovoltaic polymers by resolving their shortcomings using innovative organic synthetic approaches. It is demonstrated that the materials’ optoelectronic property as well as their fabrication process can be alternated through chemistry modification at a molecular scale, that is, by molecule engineering. This study paves a way not only to achieve high performance polymer solar cells, but also to provide novel synthetic strategies for researchers in the field to further push the boundaries of polymer solar cell technology in the future.

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