Doping and roll-to-roll processing of organic solar cells
Abstract/Contents
- Abstract
- Organic solar cells have been a subject of intense research over two decades due to the inherent advantages of very thin active layers, chemical tunability, lack of dangling bonds, and the use of abudant, non-toxic materials. Power conversion efficiencies for small-molecule and polymer solar cells have reached 8.3% and 8.1%, respectively, but many technical hurdles need to be overcome before organic solar cells can become a viable technology for large-scale power generation. Relative to silicon technology, the device physics of organic solar cells remain poorly understood. In addition, despite the promise of low-cost roll-to-roll processing, there are few examples of this manufacturing technology applied to organic solar cell active layers or the transparent conductor. This thesis covers both fundamental device physics and large-scale fabrication of thin films. In the first part of this thesis, we show that providing a strong electric field at the donor-acceptor heterointerface in organic solar cells is essential to the efficient operation of this type of solar cell. This is due to the strong Coulomb attraction between the electron and hole that are generated in close proximity upon exciton dissociation. To limit losses in electrochemical potential associated with this field, it must be concentrated near the donor-acceptor interface by n and p-doping of the acceptor and donor material, respectively. Many of the most extensively studied and efficient small molecule solar cells appear to have unintentional doping that is hard to remove. In the second part of this thesis, we demonstrate that roll-to-roll processed multilayer transparent conductors are an attractive alternative to conventional indium tin oxide (ITO). By cutting the amount of ITO used in the transparent conductor and adding a thin layer of silver, we decrease material costs as well as enable spectral tuning to enhance photocurrent density for a specific photoactive material. The multilayer anodes are fabricated on flexible plastic substrates using large-scale roll-to-roll technology, and the transmission and sheet resistance are comparable to competing technologies. Early trials of polymer solar cells deposited on these transparent conductors show promising device performance. In the third part of this thesis, we demonstrate high speed roll-to-roll vacuum deposition of a small molecular weight organic material onto a plastic substrate pre-coated with a solution-processed carbon nanotube mesh transparent electrode and hole-injection layer. A 20nm-thick layer of the molecular donor copper phthalocyanine was deposited from a custom 12" wide linear source at roll feed rates up to 2 m.min-1. The performance of the resulting devices is identical to that of devices deposited in a conventional point-source evaporator despite a 100-fold increase in deposition rate. The manufacturing throughput demonstrated at this early stage is already very competitive with CdTe and a-Si.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Copyright date | 2011 |
| Publication date | 2010, c2011; 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Liu, Albert Shih-Young |
|---|---|
| Associated with | Stanford University, Department of Materials Science and Engineering |
| Primary advisor | Peumans, Peter, 1975- |
| Primary advisor | Salleo, Alberto |
| Thesis advisor | Peumans, Peter, 1975- |
| Thesis advisor | Salleo, Alberto |
| Thesis advisor | Brongersma, Mark L |
| Advisor | Brongersma, Mark L |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Albert S. Liu. |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering. |
| Thesis | Ph.D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Albert Shih-Young Liu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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