Organic solar cells have the potential to provide low-cost photovoltaic devices as a clean and renewable energy resource. In this thesis, we focus on understanding the energy conversion process in organic solar cells, and improving the power conversion efficiencies via controlled growth of organic nanostructures.
First, we explain the unique optical and electrical properties of organic materials used for photovoltaics, and the excitonic energy conversion process in donor-acceptor heterojunction solar cells that place several limiting factors of their power conversion efficiency. Then, strategies for improving exciton diffusion and carrier collection are analyzed using dynamical Monte Carlo models for several nanostructure morphologies. Organic vapor phase deposition is used for controlling materials crystallization and film morphology. We improve the exciton diffusion efficiency while maintaining good carrier conduction in a bulk heterojunction solar cell. Further efficiency improvement is obtained in a novel nanocrystalline network structure with a thick absorbing layer, leading to the demonstration of an organic solar cell with 4.6% efficiency. In addition, solar cells using simultaneously active heterojunctions with broad spectral response are presented.
We also analyze the efficiency limits of single and multiple junction organic solar cells, and discuss the challenges facing their practical implementations.
|Advisor:||Forrest, Steven R.|
|School Location:||United States -- New Jersey|
|Source:||DAI-B 69/07, Dissertation Abstracts International|
|Subjects:||Electrical engineering, Energy, Materials science|
|Keywords:||Organic electronics, Organic vapor phase deposition, Photovoltaics, Solar cells, Thin film solar cells|
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