Optimization of organic solar cells
Abstract/Contents
- Abstract
- Organic solar cell is a promising technology because the versatility of organic materials in terms of the tunability of their electrical and optical properties and because of their relative insensitivity to film imperfections which potentially allows for very low-cost high-throughput roll-to-roll processing. However, the power conversion efficiency of organic solar cell is still limited and needs to be improved to be competitive with grid parity. In this thesis, I'll discuss major factors to limit efficiencies of bilayer organic solar cells such as light absorption, exciton diffusion and open circuit voltage. Light trapping enhances light absorption and increases efficiencies with thinner devices structure. The technique is particularly important in organic solar cells because internal quantum efficiency of organic solar cells is low with thick films while absorption is weak with thin films. V-trap configuration is a simple and effective light trapping scheme for organic solar cells since there is no need to modify active layers, thinner films achieve high efficiencies and no tracking system is necessary. The effects of total internal reflection in shaped substrates and the comparison with shapes other than V-shape will be also provided in Chapter 2. Exciton diffusion is a main bottleneck in bilayer organic solar cells and thus the exciton diffusion length (LD) is an important parameter that determines efficiency. However, different groups report different LDs because there are many factors that affect the diffusion length or because there is a systematic error in the measurement Abstract v method. The photocurrent spectroscopy method to estimate LD in Chapter 3 and the effect of molecular packing on LD will be discussed in Chapter 4. Even when light absorption and exciton diffusion are optimized, the efficiency of a single junction organic solar cell is too low for commercial applications. Multijunction cells are a way to achieve the efficiencies needed. I'll discuss the practical efficiencies of tandem organic solar cells in the case of a series-connected tandem cell and an unconstrained (multi-terminal) tandem cell. In practical cases, unconstrained tandem cells result in higher efficiencies because of the increased freedom in choosing materials and device structures without requiring current matching. Semitransparent solid state dye sensitized cells are demonstrated as a route to realize three terminal tandem cells in Chapter 5. Curved focal plane arrays on stretchable silicon mesh networks can lead to realize high performance optical system with simple design. In Chapter 6, I show that curved focal plane arrays have optical advantages such as small number of elements, bright and accurate imaging for off-axis locations. Fabrication method is briefly introduced.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Rim, Seung |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering |
| Primary advisor | Peumans, Peter, 1975- |
| Thesis advisor | Peumans, Peter, 1975- |
| Thesis advisor | McGehee, Michael |
| Thesis advisor | Wong, Hon-Sum Philip, 1959- |
| Advisor | McGehee, Michael |
| Advisor | Wong, Hon-Sum Philip, 1959- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Seung Bum Rim. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Ph.D. Stanford University 2010 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Seung Bum Rim
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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