Multicolor colloidal quantum dot based inorganic light emitting diode on silicon : design, fabrication and biomedical applications

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Title: Multicolor colloidal quantum dot based inorganic light emitting diode on silicon : design, fabrication and biomedical applications
Author: Gopal, Ashwini
Abstract: Controlled patterning of light emitting diodes on semiconductors enables a vast variety of applications such as structured illumination , large -area flexible displays , integrated optoelectronic systems and micro -total analysis systems for real time biomedical screening . We have demonstrated a series of techniques of creating quantum -based (QD ) patterned inorganic light emitting devices at room temperature on silicon (Si ) substrate . In particular : (I ) A combination of QDs self -assembly and microcontact printing techniques were developed to form the light emission monolayer . We expand the self -assembly method with the traditional Langmuir -Schaeffer technique to rapidly deposit monolayers of core : shell quantum dots on flat substrates . A uniform film of QDs self -assembled on water was transferred using hydrophobic polydimethylsiloxane stamps with various nano /micro -scale patterns , and was subsequently stamped . A metal oxide electron transport layer was co -sputtered onto the QDs . The structure was completed by an e -beam evaporating thin metal cathode . Multicolor light emission was observed on application of voltage across the device . (II ) We also demonstrate the photolithographic patterning capability of a metal cathode for top emitting QDLEDs on Si substrates . Lithographic patterning technique enables site -controlled patterning and controlled feature size of the electrode with greater accuracy . The stability of inorganic silicon materials and metal oxide based diode structure offers excellent advantages to the device , with no significant damage observed during the patterning and etching steps . Efficient electrical excitation of QDs was demonstrated by both the methods described above . The technique was translated to create localized QD -based light sources for two applications : (1 ) Three -dimensional scanning probe tip structures for near field imaging . Combined topographic and optical images were acquired using this new class of “self -illuminating” probe in commercial NSOM . The emission wavelength can be tuned through quantum -size effect of QDs . (2 ) Multispectral excitation sources integrated with microfluidic channels for tumor cell analyses . We were able to detect the variation of sub -cellular features , such as the nucleus -to -cytoplasm ratio , to quantify the absorption at different wavelength upon the near -field illumination of individual tumor cells towards the determination of cancer developmental stage .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2209
Date: 2011-02-07

Citation

Multicolor colloidal quantum dot based inorganic light emitting diode on silicon : design, fabrication and biomedical applications. Doctoral dissertation, University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2209 .

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