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Inorganic-Organic Hybrid Technology for Light Emitting Diodes
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. (Organic electronics)
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Since the first report of inorganic light emtting diodes a century ago the field of inorganic light emitting diodes has evolved rapidly. T he development of light emitting diodes technology has caused their efficiency and light output to increase exponentially, with a doubling occuring about every 36 months  since the 1960s, in a similar way to Moor´s law. the advances are generally attributed to the parallel development of the semiconductor technologies and advances in optics and material science. This trend is normally called Haitz´s law after Dr. Roland Haitz.

on the other hand, during the last 30 years a new research and technology field of organic electronic materials has grown. Organic light emitting diodes is rapidly maturing for the development of large area light -emitting displays. The reasons behind that is the possibility of using uconventional substrates such as flexible plastic and glass and the availability of several very cheap production methods.

This thesis deals with the demonstration and investigation of heterjuction light emitting diodes (LEDs) based on n-ZnO-nanorod/p-polymer hybrid layered structures. The devices were fabricated using low cost and flexible substrates (glass and plastic substrates). Both ZnO-nanorods and the polymer materials were grown using low temperature methods. Different configurations were used starting with single polymer emissive layer ending up with separate emissive and blocking layers. In addition, blend multilayer structures were also used. In each case the advantages and disadvantages were investigated. analyzed and discussed. In general room temperature photoluminescence and electroluminescence spectra of the LEDs provided a broad emission band covering a wide color range (430nm- 700nm), in which zinc vacancies, oxygen vacancies and polymer emission peaks are contributting to the observed broad emission.

Place, publisher, year, edition, pages
Liu Tryck: Linköping University Electronic Press , 2009. , 48 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1395
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-51600Local ID: LiU-TEK-LIC-2009:3ISBN: 978-91-7393-688-0 (print)OAI: oai:DiVA.org:liu-51600DiVA: diva2:275956
Presentation
2009-02-13, Campus Norrköping, Linköpings universitet, Norrköping, 09:00 (English)
Opponent
Supervisors
Available from: 2010-01-25 Created: 2009-11-09 Last updated: 2014-01-15Bibliographically approved
List of papers
1. The demonstration of hybrid n-ZnO nanorod/p-polymer heterojunction light emitting diodes on glass substrates
Open this publication in new window or tab >>The demonstration of hybrid n-ZnO nanorod/p-polymer heterojunction light emitting diodes on glass substrates
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2009 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 95, no 3, 807-812 p.Article in journal (Refereed) Published
Abstract [en]

We report a demonstration of heterojunction light emitting diode (LED) based on a hybrid n-ZnO-nanorod/p-polymer layered structure. The ZnO was grown using the aqueous chemical growth (ACG) on top of the polymer(s) which were deposited on glass. The current-voltage (I-V) behavior of the heterojunctions showed good rectifying diode characteristics. Room-temperature electroluminescence (EL) spectra of the LEDs provided a broad emission band over a wide LED color range (430-650 nm), in which both zinc and oxygen vacancy peaks are clearly detected. We present here luminescent devices based on the use of ZnO-nanorods in combination with two different blended and multi-layered p-type polymers. Electroluminescence of the first batch of devices showed that white bluish strong emission for the presently used polymers is clearly observed. We obtained a turn-on voltage of 3 V and break-down voltage equal to -6 V for PVK-TFB blended device. The corresponding values for the NPD-PFO multilayer device were 4 V and -14 V, respectively. The rectification factors were equal to 3 and 10 for the two devices, respectively. The films and devices processed were characterized by scanning electron microscopy (SEM), DEKTAK 3ST Surface Profile, Semiconductor Parameter Analyzer, photoluminescence (PL), and electroluminescence (EL).

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17910 (URN)10.1007/s00339-009-5075-8 (DOI)
Available from: 2009-04-26 Created: 2009-04-24 Last updated: 2017-12-13Bibliographically approved
2. The effect of the interlayer design on the electroluminescence and electrical properties of n-ZnO nanorod/p-type blended polymer hybrid light emitting diodes
Open this publication in new window or tab >>The effect of the interlayer design on the electroluminescence and electrical properties of n-ZnO nanorod/p-type blended polymer hybrid light emitting diodes
2009 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 6, 065710- p.Article in journal (Refereed) Published
Abstract [en]

Hybrid light emitting diodes (LEDs) based on n-ZnO nanorods and blended polymers were fabricated and characterized. The blended polymers consisted of a blue emitting polymer and a charge transport polymer. The effect of the interlayer design on the electrical and electroluminescent characteristics of these hybrid LEDs was investigated. We demonstrated that by adding a calcium (2) acetylacetonate [Ca(acac)(2)] layer between the blended polymer layer and the ZnO nanorods, an increase in device performance was observed. The purpose of the extra layer was to act as a band offset stepping layer (offset divider). Moreover, the effect of the stepper layer thickness for this offset stepping layer was studied. The results indicate that LED performance is greatly affected by the presence and thickness of this band offset stepping layer.

Keyword
ZnO-nanorods, p-type polymer, LEDs
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-16614 (URN)10.1088/0957-4484/20/6/065710 (DOI)
Note
Original Publication: Amal Wadesa, Omer Nour and Magnus Willander, The effect of the interlayer design on the electroluminescence and electrical properties of n-ZnO nanorod/p-type blended polymer hybrid light emitting diodes, 2009, NANOTECHNOLOGY, (20), 6, 065710. http://dx.doi.org/10.1088/0957-4484/20/6/065710 Copyright: Institute of Physics http://www.iop.org/ Available from: 2009-02-11 Created: 2009-02-06 Last updated: 2017-12-14Bibliographically approved
3. Solution processed ZnO nanorods/polyfluorene semiconductor heterojunctions with white light photoluminescence
Open this publication in new window or tab >>Solution processed ZnO nanorods/polyfluorene semiconductor heterojunctions with white light photoluminescence
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Hybrid inorganic-organic semiconductor heterojunctions are nowadays scrutinized for optoelectronic devices, such as solar cells and light emitting diodes. Here, ZnOnanorods/ polyfluorene heterojunctions have been entirely fabricated from solution by wet chemistry and low temperature processes. The morphology of the polyfluorene film appears to be an important parameter to control the growth of the ZnO nanorods and affects their optical properties. The visible emission of the conjugated polymer and the ZnO are complementary and provide a broad emission in the visible. Because of its solution processability and broad emission, the ZnO/polyfluorene heterojunction is promising for large area white lightning applications.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-53586 (URN)
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2014-01-15

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