Novel ultraviolet scintillators based on semiconductor quantum dot emitters for significantly enhanced photodetection and photovoltaics
Author
Mutlugün, Evren
Advisor
Demir, Hilmi Volkan
Date
2007Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Silicon photonics opens opportunities to realize optoelectronic devices directly
on large-scale integrated electronics, leveraging advanced Si fabrication and
computation capabilities. However, silicon is constrained in different aspects for
use in optoelectronics. Such one limitation is observed in Si based
photodetectors, cameras, and solar cells that exhibit very poor responsivity in
the ultraviolet (UV) spectral range. Si CMOS photodetectors and CCD cameras
cannot be operated in UV, despite the strong demand for UV detection and
imaging in security applications. Also, although 95% of the photovoltaics
market is dominated by Si based solar cells, silicon is not capable of using UV
radiation of the solar spectrum for solar energy conversion, as required
especially in space applications. In this thesis for the first time, we demonstrate
novel UV scintillators made of semiconductor quantum dot emitters hybridized
on Si detectors and cameras to detect and image in UV with significantly
improved responsivity and on Si solar cells to generate electrical energy from
UV radiation with significantly improved solar conversion efficiency. We
present the device conception, design, fabrication, experimental
characterization, and theoretical analysis of these UV nanocrystal scintillators. Integrating highly luminescent CdSe/ZnS core-shell nanocrystals, we
demonstrate hybrid photodetectors that exhibit two-orders-of-magnitude peak
enhancement in their responsivity. We also develop photovoltaic nanocrystal
scintillators to enhance open-circuit voltage, short-circuit current, fill factor, and
solar conversion efficiency in UV. Hybridizing CdSe/ZnS quantum dots on Si
photovoltaic devices, we show that the solar conversion efficiency is doubled
under white light illumination (Xe lamp). Such UV scintillator nanocrystals
hold great promise to enable photodetection and imaging in UV and extend
photovoltaic activity to UV.
Keywords
Nanocrystalsultraviolet
solar conversion efficiency
photocurrent
solar cells,
photovoltaics
cameras
photodetectors
Si
responsivity
scintillators
quantum dots