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Electrical and Computer Engineering

Electrical, Computer & Energy Engineering Graduate Theses & Dissertations

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Exceeding Conventional Photovoltaic Efficiency Limits Using Colloidal Quantum Dots, Gregory F. Pach Apr 2017

Exceeding Conventional Photovoltaic Efficiency Limits Using Colloidal Quantum Dots, Gregory F. Pach

Electrical, Computer & Energy Engineering Graduate Theses & Dissertations

Colloidal quantum dots (QDs) are a widely investigated field of research due to their highly tunable nature in which the optical and electronic properties of the nanocrystal can be manipulated by merely changing the nanocrystal’s size. Specifically, colloidal quantum dot solar cells (QDSCs) have become a promising candidate for future generation photovoltaic technology. Quantum dots exhibit multiple exciton generation (MEG) in which multiple electron-hole pairs are generated from a single high-energy photon. This process is not observed in bulk-like semiconductors and allows for QDSCs to achieve theoretical efficiency limits above the standard single-junction Shockley-Queisser limit. However, the fast expanding ...


Graphene-Semiconductor Heterojunctions And Devices, Tzu-Min Ou Apr 2015

Graphene-Semiconductor Heterojunctions And Devices, Tzu-Min Ou

Electrical, Computer & Energy Engineering Graduate Theses & Dissertations

In this thesis we explore the potential of versatile graphene-semiconductor heterojunctions in photodetection and field-effect transistor (FET) applications. The first part of the thesis studies near-infrared photodiode (NIR PD) based on a graphene- n-Si heterojunction in which graphene is used as the absorbing medium. Graphene is chosen for its absorption in NIR wavelengths to which Si is not responsive. Most graphene detectors in the literature are photoconductors that have a high dark current. The graphene-Si heterojunction PD has a large Schottky barrier height that suppresses the dark current and enhances the current rectification and the photon detectivity.

The fabricated graphene-Si ...


Graphene Geometric Diodes For Optical Rectennas, Zixu James Zhu Jul 2014

Graphene Geometric Diodes For Optical Rectennas, Zixu James Zhu

Electrical, Computer & Energy Engineering Graduate Theses & Dissertations

Optical rectennas, which are micro-antennas to convert optical-frequency radiation to alternating current combined with ultrahigh-speed diodes to rectify the current, can in principle provide high conversion efficiency solar cells and sensitive detectors. Currently investigated optical rectennas using metal/insulator/metal (MIM) diodes are limited in their RC response time and poor impedance matching between diodes and antennas. A new rectifier, the geometric diode, can overcome these limitations. The thesis work has been to develop geometric diode rectennas, along with improving fabrication processes for MIM diode rectennas. The geometric diode consists of a conducting thin-film, currently graphene, patterned into a geometry ...