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Nano-Optics-Enabled High-Efficiency Solar Cells

Kim, Myungji (2014) Nano-Optics-Enabled High-Efficiency Solar Cells. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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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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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairKim, Hong Koohkk@pitt.eduHKK
Committee MemberLanger, Dietrich Wdwl@pitt.eduDWL
Committee MemberStanchina, William Ewes25@pitt.eduWES25
Committee MemberLi, Guangyonggul6@pitt.eduGUL6
Committee MemberMcDermott, Thomas Etem42@pitt.eduTEM42
Committee MemberCho, Sung Kwonskcho@pitt.eduSKCHO
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


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