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Control of Photoelectron Kinetics to Improve Performance of Quantum Dot-Based Optoelectronic Devices
Başlık:
Control of Photoelectron Kinetics to Improve Performance of Quantum Dot-Based Optoelectronic Devices
Yazar:
Joseph Varghese, Alex, author.
ISBN:
9780438004368
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (114 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Serge Oktyabrsky Committee members: Hassaram Bakhru; Harry Efstathiadis; Vincent LaBella; Gopal Pethuraja.
Özet:
The topic of my dissertation is to find technological methods to control photocarrier kinetics in quantum dot infrared photodetectors and quantum dot solar cells. Quantum dot infrared photodetectors can be used in various applications like night infrared vision, search and rescue, space surveillance and medical diagnostics. However photoconductive detectors suffer from short photocarrier lifetime, that drastically reduces the photocurrent and limits the operation temperature. This also affects the responsivity and detectivity of the detector. Suppression of photoelectron capture can be realized by adjusting the potential barriers around the quantum dots, which spatially separates the localized states from the continuum. Potential barriers are formed when electrons populating the dots are taken from nearby doped layers (modulation interdot doping). For the first part of my dissertation, I will be focusing on the effect of tuning the electrostatic potential barrier by four means: (1) by changing the number of electrons in a quantum dot; (2) by varying the spacing between the quantum dot planes; (3) by modifying shape of quantum dots (4) by varying the number of electrons in quantum dot by complex bipolar doping (with acceptor doping directly into the dots and donors between the QD layers). These approaches suppress the photoelectron capture and improve the performance of the detectors.
For the second part of my dissertation, I will focus on using nanostructured III-V semiconductors for improving power conversion efficiency of single junction GaAs solar cell. For the past few years significant progress has been achieved in improving the efficiency of solar cells using various approaches like multi-junction solar cells and concentrated photovoltaics. In another set of approaches, a narrow-bandgap material is inserted into p-n junction to harvest infrared solar radiation. The examples of proposed structures include an intermediate band solar cell and quantum dot enhanced solar cells. Single-junction IR harvesting can theoretically improve the efficiency to 63% from Shockley-Quiesser limit of 33.7%. However, so far just minor efficiency improvements were experimentally demonstrated. Typically, the increase in short circuit current (Jsc) due to the IR absorption of sub band gap photons is accompanied with a decrease in operation voltage. Using molecular beam epitaxially grown material, the predicted effects of wetting layer on IR absorption and photocarrier recombination are proposed. The improvement of efficiency is envisioned through engineering the growth of quantum dots to achieve complete voltage (Voc) recovery.
Notlar:
School code: 0668
Mevcut:*
Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(680574.1) | 680574-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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