Dr. Harry L. Kwok Profile

Dr. Harry L. Kwok

Professor at Univ of Victoria

SPIE Involvement:

Author

Proceedings Article | 29 August 2017 Paper

A model for exciton formation in organic electroluminescent devices

H. Kwok

Proceedings Volume 10313, 103133D (2017) https://doi.org/10.1117/12.2283917

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Proceedings Article | 13 September 2007 Paper

Current conduction in ambipolar organic field-effect transistors (OFETs)

H. Kwok

Proceedings Volume 6658, 66580E (2007) https://doi.org/10.1117/12.730486

KEYWORDS: Field effect transistors, Transistors, Polarons, Semiconductors, Oxides, Interfaces, Capacitance, Silver, Dielectrics, Organic semiconductors

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Proceedings Article | 14 September 2006 Paper

Charge relaxation and dynamics in organic semiconductors

H. Kwok

Proceedings Volume 6320, 63200I (2006) https://doi.org/10.1117/12.673715

KEYWORDS: Solids, Organic semiconductors, Data modeling, Solid modeling, Crystals, Picosecond phenomena, Code division multiplexing, Statistical analysis, Molecular interactions, Statistical modeling

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Proceedings Article | 12 September 2006 Paper

Evaluation of inorganic and organic light-emitting diode displays for signage application

Harry Kwok, Pratibha Sharma

Proceedings Volume 6337, 63371K (2006) https://doi.org/10.1117/12.680123

KEYWORDS: Organic light emitting diodes, Light emitting diodes, Reflectivity, LED displays, OLED lighting, Coating, Manufacturing, Lamps, Diffusers, Light sources

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High-brightness, inorganic light-emitting diodes (LEDs) have been successfully utilized for edge-lighting of large displays for signage. Further interest in solid-state lighting technology has been fueled with the emergence of small molecule and polymer-based organic light-emitting diodes (OLEDs). In this paper, edgelit inorganic LED-based displays and state-of-the-art OLED-based displays are evaluated on the basis of electrical and photometric measurements. The reference size for a signage system is assumed to be 600 mm x 600mm based on the industrial usage. With the availability of high power light-emitting diodes, it is possible to develop edgelit signage systems of the standard size. These displays possess an efficacy of 18 lm/W. Although, these displays are environmentally friendly and efficient, they suffer from some inherent limitations. Homogeneity of displays, which is a prime requirement for illuminated signs, is not accomplished. A standard deviation of 3.12 lux is observed between the illuminance values on the surface of the display. In order to distribute light effectively, reflective gratings are employed. Reflective gratings aid in reducing the problem but fail to eliminate it. In addition, the overall cost of signage is increased by 50% with the use of these additional components. This problem can be overcome by the use of a distributed source of light. Hence, the organic-LEDs are considered as a possible contender. In this paper, we experimentally determine the feasibility of using OLEDs for signage applications and compare their performance with inorganic LEDs. Passive matrix, small-molecule based, commercially available OLEDs is used. Design techniques for implementation of displays using organic LEDs are also discussed. It is determined that tiled displays based on organic LEDs possess better uniformity than the inorganic LED-based displays. However, the currently available OLEDs have lower light-conversion efficiency and higher costs than the conventional, inorganic LEDs. But, signage panels based on OLEDs can be made cheaper by avoiding the use of acrylic sheet and reflective gratings. Moreover, the distributed light output and light weight of OLEDs and the potential to be built inexpensively on flexible substrates can make OLEDs more beneficial for future signage applications than the inorganic LEDs.

Proceedings Article | 24 July 2006 Paper

Design and implementation of organic LED-based displays for signage application

Pratibha Sharma, Harry Kwok

Proceedings Volume 6342, 63422O (2006) https://doi.org/10.1117/12.692215

KEYWORDS: Organic light emitting diodes, Reflectivity, Coating, OLED lighting, Fourier transforms, Light sources, Reflection, Optical testing, Manufacturing, LCDs

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Proceedings Article | 16 September 2005 Paper

Evaluation of the field-effect carrier mobility in single-grain (and polycrystalline) organic semconductors

H. Kwok

Proceedings Volume 5924, 59240P (2005) https://doi.org/10.1117/12.611395

KEYWORDS: Field effect transistors, Organic semiconductors, Transistors, Temperature metrology, Oxides, Thin film devices, Semiconductors, Code division multiplexing, Solids, Crystals

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Proceedings Article | 28 June 2005 Paper

Investigation into the modeling of field-effect mobility in disordered organic semiconductors

H. Kwok

Proceedings Volume 5838, (2005) https://doi.org/10.1117/12.605541

KEYWORDS: Code division multiplexing, Organic semiconductors, Field effect transistors, Data modeling, Crystals, Electronic components, Semiconductors, Temperature metrology, Statistical modeling, Instrument modeling

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Proceedings Article | 2 August 2004 Paper

Bias and temperature effect on the carrier transport parameters in impedance spectroscopy

Harry Kwok

Proceedings Volume 5508, (2004) https://doi.org/10.1117/12.552726

KEYWORDS: Capacitance, Dielectric spectroscopy, Organic semiconductors, Solids, Image processing, Polymers, Light emitting diodes, Aluminum, Calcium, Plasma

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Proceedings Article | 9 July 2003 Paper

Space charge effect in organic light-emitting devices (OLEDs)

Harry Kwok

Proceedings Volume 5218, (2003) https://doi.org/10.1117/12.505781

KEYWORDS: Organic light emitting diodes, Organic semiconductors, Excitons, Diffusion, Semiconductors, Data modeling, Dielectrics, Electrodes, Doping, Interfaces

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