Kim, Myungji
(2014)
Nano-Optics-Enabled High-Efficiency Solar Cells.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Glancing angle coupling of light into dielectric media is a desirable feature that can benefit the performance of solar cells. At a highly refractive dielectric interface, however, the transmission angle is limited small (e.g., ~15 deg for air/Si) by Snell’s law. In this thesis, we propose a new method of light coupling that overcomes the conventional limits of refractive transmission. A vertical dipole structure is designed to enable glancing propagation into high-index media, enhancing light absorption and carrier collection for a given thickness of active medium. A vertical-dipole nano-optic structure was introduced to a conventional finished silicon cell (~16% efficiency). The vertical dipoles reradiate incident light into oblique directions inside the active medium (Si). The glancing propagation along the junction interface results in a synergistic, uncompromised improvement of cell performance (i.e., enhancing photocarrier generation without sacrificing carrier transport) and demonstrates 20% cell efficiency. We have further studied low-voltage, broadband photocarrier multiplication in a graphene/SiO2/Si structure and demonstrate external quantum efficiency 146-200% (internal quantum efficiency 218-384%) as measured with photocurrent in UV-to-NIR (325-850nm). The self-induced electric field (~106 V/cm) in 2D electron gas enables impact ionization at low bias (< 2V), in a way promising and compatible with photovoltaic operation.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
22 September 2014 |
| Date Type: |
Publication |
| Defense Date: |
2 July 2014 |
| Approval Date: |
22 September 2014 |
| Submission Date: |
22 July 2014 |
| Access Restriction: |
5 year -- Restrict access to University of Pittsburgh for a period of 5 years. |
| Number of Pages: |
150 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Electrical and Computer Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Photovoltaics, electronic device, solar cell, photo carrier multiplication |
| Date Deposited: |
22 Sep 2015 05:00 |
| Last Modified: |
22 Sep 2019 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/22461 |
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