Luminescence: Basic Concepts, Applications and Instrumentation

276 Pages·2014·15.558 MB·English

by  H. S. Virk

Luminescence

Basic Concepts,
Applications
and Instrumentation
Edited by
Hardev Singh Virk
Luminescence

Basic Concepts, Applications
and Instrumentation
Special topic volume with invited peer reviewed papers only.
Edited by
Hardev Singh Virk
Copyright  2014 Trans Tech Publications Ltd, Switzerland

All rights reserved. No part of the contents of this publication may be reproduced or
transmitted in any form or by any means without the written permission of the
publisher.

Trans Tech Publications Ltd
Churerstrasse 20
CH-8808 Pfaffikon
Switzerland
http://www.ttp.net

Volume 357 of
Defect and Diffusion Forum
ISSN print 1012-0386
ISSN cd 1662-9515
ISSN web 1662-9507

(Pt. A of Diffusion and Defect Data – Solid State Data ISSN 0377-6883)
Full text available online at http://www.scientific.net

Distributed worldwide by and in the Americas by
Trans Tech Publications Ltd Trans Tech Publications Inc.
Churerstrasse 20 PO Box 699, May Street
CH-8808 Pfaffikon Enfield, NH 03748
Switzerland USA
Phone: [phone]
Fax: [phone] Fax: [phone]
e-mail: [e-mail] e-mail: [e-mail]
Editor’s Note
The word luminescence was first used by a German physicist, Eilhardt Wiedemann, in 1888.
He also classified luminescence into six kinds according to the method of excitation. No
better basis of classification is available today. He recognized photoluminescence,
thermoluminescence, electroluminescence, crystalloluminescence, triboluminescence, and
chemiluminescence. The designations are obvious, characterized by the prefix.
This Volume consists of 9 Chapters, including 8 Review Papers and one Case Study. The
first two papers are based on OLEDs. Organic light emitting diodes (OLEDs) have been the
focus of intense study since the late 1980s. Since that time, research has continued to
demonstrate the potential of OLEDs as viable systems for displays and eco-friendly lighting
applications. Thejokalyani and Sanjay Dhoble have given historical introduction to OLEDs in
the first chapter under the title “Importance of Eco-friendly OLED Lighting”. They describe
core fabrication technologies and applications of OLEDs in their paper. V. K. Chandra et al.
have covered both theoretical and experimental aspects in their paper, “Organic Light -
Emitting Diodes and their Applications” in the most rigorous way. This Chapter describes the
salient features of OLEDs and discusses the applications of OLEDs in displays and solid state
lighting devices.

Organic-inorganic hybrid nanocomposite materials have been of great interest for their
extraordinary performances. Interaction between the polymer matrix and nanocrystalline
fillers produces wonderful features, viz. thermal, magnetic, mechanical, electrical and optical
properties to these materials. S.K. Tripathi et al. have reviewed the present status of II-VI
polymer nanocomposites from the photoluminescence studies point of view in the 3rd
Chapter. Electroluminescence in undoped and doped chalcogenide nanocrystals and
nanocomposites is reviewed in 4th Chapter by Meera et al. Nanocrystalline powder samples
of CdS, CdSe, ZnS and ZnSe nanocrystals and their composites with PVA and PVK have
been prepared by chemical route and investigated in detail. Chapters 5 and 6 are contributed
by RK Gartia on two important topics: “Thermoluminescence of Persistent Luminescent
Materials” and “Design of Inorganic Scintillators: Role of Thermoluminescence”. The author
has demonstrated the application of TL, by virtue of its inherent sensitivity coupled with its
universal applicability, to investigate practically all semiconducting/inorganic materials in
terms of their trap- spectroscopy.
Chapter 7 by Rabiul Biswas deals with application of luminescence to earth and planetary
sciences. The author discusses some landmarks and recent developments in this field of
luminescence dating with stress on extending the dating range. Chapter 8 by Jain and Bøtter-
Jensen is focused on the developments around the Risø-TL/OSL reader which is popular
amongst the dating community. The 9th Chapter is added as a case study. The authors, JN
Reddy and KVR Murthy, claim that the primary objective of their PC Controlled TL Reader
is to bring out versatile TL instrumentation system and also to make it affordable to many of
the researchers in the Universities and other areas, including Radio-therapy and Medical
Physics.

Editor thanks all the authors for their valuable contributions and reviewers for their timely
help. Trans Tech Publishers deserve my appreciation for bringing out this volume in time.

H.S. Virk
Editor
Table of Contents
Editor's Note
Importance of Eco-Friendly OLED Lighting
N. Thejokalyani and S.J. Dhoble 1
Organic Light - Emitting Diodes and their Applications
V.K. Chandra, B.P. Chandra and P. Jha 29
Photoluminescence Studies in II-VI Nanoparticles Embedded in Polymer Matrix
S.K. Tripathi, J. Kaur and R. Kaur 95
Electroluminescence in Chalcogenide Nanocrystals and Nanocomposites
M. Ramrakhiani, N. Gautam, K. Kushwaha, S. Sahare and P. Singh 127
Thermoluminescence of Persistent Luminescent Materials
R.K. Gartia and N. Chandrasekhar 171
Design of Inorganic Scintillators: Role of Thermoluminescence
R.K. Gartia 193
Development and Application of Luminescence to Earth and Planetary Sciences: Some
Landmarks
R.H. Biswas 217
Luminescence Instrumentation
M. Jain and L. Bøtter-Jensen 245
TLD Instrumentation: A Case Study of PC Controlled TL Reader
J.N. Reddy and K.V.R. Murthy 261
Defect and Diffusion Forum Vol. 357 (2014) pp 1-27
© (2014) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/DDF.357.1
Importance of Eco-friendly OLED Lighting
N. Thejokalyani1,a and S.J. Dhoble2,b
1Department of Applied Physics, Laxminarayan Institute of Technology, Nagpur-440033, India
2Department of Physics, R.T.M. Nagpur University, Nagpur-440033, India
[e-mail], [e-mail] (Corresponding author)

Keywords: Artificial lighting, Eco-friendly, Energy efficient, Solid-state lighting, OLEDs
Abstract. The importance of artificial light has long been recognized as it extends the day. Copious
corporations and academic institutions are investing cosmic treasures in tracking down the
advanced artificial lighting applications with a vision towards energy efficient and eco-friendly
solid state lighting. In this regard, organic light-emitting diodes (OLEDs) are going to change the
human lifestyle, by offering a promising avenue to develop future energy saving solid-state lighting
sources because of their intrinsic characteristics such as low driving voltage, high resolution, high
brightness, large viewing angle, large color gamut, high contrast, less weight and size, efficiency
etc., there by dictating their ability to reach the pinnacle in the field of flat panel displays and solid
state lighting sources. With the goal towards future application, many design strategies like
synthesis of novel materials, well judged anatomy of device configuration, development of refined
and low cost fabrication techniques have been put forward to achieve high efficiency, good color
stability and quality lighting. Practical applications, which enrich the ideas of the specialists in this
field to develop new routes for future research development of OLEDs are enumerated and
illustrated by specific examples. This chapter also integrates the novel approaches for energy
efficient and eco-friendly solid state lighting as well as the limitations and global haphazards of
currently used lighting systems. The current state of the art, ongoing challenges and future
perspectives of this research frontier to reduce the driving voltage, minimization of degradation
issues, enhance their life time are illustrated. Review on the status and future outlook of these
OLEDs strongly reveals their emergence in the next few years.
Contents of Paper
1. Light
2. Lighting
2.1. Natural Lighting
2.2. Artificial Lighting
3. Classification of Lighting
3.1. Task Lighting
3.2. Accent Lighting
3.3. Ambient Lighting
4. Lighting Terms
4.1. Luminaire
4.2. Luminaire Efficiency
4.3. Luminance
4.4. Luminous Flux
4.5. Luminous Efficacy
4.6. Lumen
4.7. Illuminance
4.8. Lux
5. History of Lighting
6. Time-line of Artificial Lighting Technology
6.1. Fire
6.2. Kerosene-oil Lamps
2 Luminescence
6.3. Incandescent Lamps
6.4. Fluorescent Lamps
6.5. Compact Fluorescent Lamps (CFLs)
7. Solid State Lighting (SSL)
7.1. Color Rendering Index (CRI)
7.2. Correlated Color Temperature (CCT)
7.3. CIE Co-ordinates
7.4. Light Emitting Diodes (LEDs)
7.5. Organic Light Emitting Diodes (OLEDs)
8. OLEDs -The Emerging Displays
8.1. Organic Semiconductors
8.2. HOMO and LUMO in Organic Semiconductors
8.3. Electronic Excitation in Organic Molecules
8.4. Types of Absorbing Electrons
8.5. OLED Anatomy
8.6. Materials for Different Layers of OLEDs
8.7. Light Emitting Mechanism from OLED Device
9. Core Fabrication Technologies
9.1. Vacuum Thermal Evaporation
9.2. Physical Vacuum Deposition
9.3. Solution Techniques
9.4. Spin-coating
9.5. Ink-jet Printing
9.6. Screen Printing
10. Encapsulation
11. Bouquets and Brickbats
12. Research Challenges Ahead
13. Applications of OLEDs and Displays
14. Conclusions
References

1. Light

Light is a physical quantity which is emitted by a luminous body and when incident on the eye
causes the sensation of sight through nerves. It is electromagnetic radiation that is visible to the
human eyes. It constitutes a tiny proportion of the whole electromagnetic spectrum. It extends from
deepest violet to the deepest red ranging between 400 nm - 800 nm. Light travels in the form of
wave, characterized by frequency and wavelength. According to the wavelength and frequency, the
color of light also changes and hence a spectrum of VIBGYOR can be observed. In VIBGYOR red
occupies more space and hence reaches our eyes first. RGB occupies two-third of the spectrum and
combination of which gives white light. Visible spectrum, its wavelength range and band width of
different colors of VIS spectrum are shown in Fig. 1 and Table 1, respectively.

Fig.1: Visible spectrum [1]
Defect and Diffusion Forum Vol. 357 3
Table 1: Wavelength range and band width of different colors of visible spectrum

Colour Wavelength range Band width
(nm) (nm)

Red 620 - 800 nm 180
Orange 580 - 600 nm 20
Yellow 560 - 580 nm 20

Green 490 - 560 nm 70
Blue 430 - 490 nm 60

Indigo 415- 430 nm 15
Violet 400 - 415nm 15
2. Lighting
Lighting is the application of light. It is the purposeful use of light to attain a realistic visual effect.
Lighting includes the use of both artificial light sources like lamps, light fittings etc. and natural day
light emitted by the sun. Lighting is a basic human need like clean water, food, sanitation and
shelter. In this new era of information technology, lighting can be considered as the basic human
right. Lighting can enhance task performance; improve the look of an area. Even today one-third of
humanity still has no access to electricity; they live in darkness after sunset. This stands as a
significant barrier to the human development. They use fuel based lighting as an alternative source
of electricity. Such lighting offers poor level of illumination and leads to health disorders. The
quality of life of millions of people around the world can have a tremendous change by the new
eco-friendly and energy efficient Solid state lighting (SSL). In developing countries, delivering SSL
to the people who are in need is a great challenge [1, 2].
2.1. Natural Lighting. Light emitted by the sun is considered as natural lighting. Lighting obtained
from sun is the most abundant source of natural lighting available in nature. Day lighting is the
oldest method of interior lighting. Use of this natural day lighting in an effective manner simply
decreases the cost and energy consumption during day time. Due to a lack of information that
indicate the likely energy savings, day lighting schemes are not yet popular among most buildings
[3-4].
2.2. Artificial Lighting. The importance of artificial light to humans and human society has long
been recognized. It is a significant factor contributing to the quality and productivity of human life.
Though fire was used by our primate ancestors 2–6 million years ago, it is still thought of as the
quintessential human invention. Indeed, artificial light is so integrated [5] into the human lifestyle
as to be barely noticeable. Artificial light extends the day and enables us to extend our work at night
[6]. It consumes a significant part of all electrical energy consumed worldwide. Around 33% of
total energy consumed is due to lighting [7]. It is valuable to provide the correct light intensity and
color spectrum for each task or environment. Otherwise, this artificial energy could not only be
wasted but over illumination can lead to adverse health and psychological effects. Light pollution is
one of the growing problems, which involves the emission of carbon dioxide from some artificial
lamps [8, 9].
3. Classification of Lighting
Based on the purpose, distribution of the light produced by the fixture and applications, lighting is
classified as task lighting, accent lighting and ambient lighting.
3.1. Task Lighting. This type of lighting helps us to perform specific tasks such as reading, sewing,
cooking, homework, hobbies, games, surgical procedures with lighting levels up to 1500 lux. Such
lighting is provided by lower-level track lighting, pendant lighting, and portable lamps. Task
lighting should be free of disturbing glare and shadows and bright enough to prevent eye strain.
4 Luminescence
3.2. Accent Lighting. This type of lighting is mainly used for decorative purposes, interior
designing and landscaping. As a part of a decorating design, it is used to spotlight paintings, house
plants, sculpture, to highlight the texture of a wall, outdoor landscaping etc. It requires at least three
times as much light on the focal point as the general lighting around it. Such lighting is provided by
track, recessed or wall-mounted fixtures.
3.3. Ambient Lighting. This type of lighting is mainly used for general illumination of an area. It
radiates comfortable level of brightness. It is also known as general lighting. It can be accomplished
with ceiling or wall-mounted fixtures, track lights, and lanterns.
4. Lighting Terms
Various terminologies used in lighting are illustrated below:
4.1 Luminaire. A luminaire is a complete lighting unit, consisting of lamp housing, ballast, sockets
and any other necessary components placed together.
4.2. Luminaire Efficiency. The ratio of lumens emitted by a luminaire to the total lumens emitted
from the light source within the luminaire is known as luminaire efficiency.
4.3. Luminance. It is a measure of the density of luminous intensity in particular direction. It
describes the amount of light that passes through or emitted from a particular area within a given
solid angle. The SI unit for luminance is candela/m2, while its CGS unit is stilb.
1 stilb1 Candela / cm2
4.4. Luminous Flux. This is the quantity of useful light emitted by a light source, measured in
lumen (lm).
4.5. Luminous Efficacy. It measures the amount of usable light emanating from the fixture per
used energy, i.e., it measures the conversion efficiency (electricity into visible light) of the source; it
is expressed in lumen/watt. Efficacy is higher for transparent lighting fixtures.
4.6. Lumen. It is a measure of the total amount of visible light emitted by a light source. It is a unit
to measure the output of visible light. This unit only quantifies the visible radiation, and excludes
invisible infrared and ultraviolet light [10].
4.7. Illuminance. It is defined as the light arriving at a surface, expressed in lumens per unit area,
measured in lux.
4.8. Lux. This is the quantity of light falling on a unit area of a surface.
1 lux1 lumen / m2
5. History of Lighting
In ancient days artificial lighting started with the discovery of fire. Later, a hollow rock, shell was
filled with animal fat, and ignited. Wicks were later added to control the rate of burning. In 18th
century, the central burner, a major improvement in lamp design, was invented by Ami Argand, a
Swiss chemist. Small glass chimneys were added to lamps to protect the flame as well as to control
the flow of air to the flame. Later coal, natural gas and kerosene lamps grew popular. First
commercial use of gas lighting began in 1792. Electric carbon arc lamp was invented later in 1801.
The invention of the incandescent light bulb has a history spanning from the early 1800s. With the
development of electricity and the incandescent light bulb, the luminosity of artificial lighting
improved and became popular for indoors. They became widely popular and extended the working
time of the people. However, only about 15% of the consumed energy is emitted in the form of light
and the rest as heat. Incandescent lamps are the least expensive to buy but the most expensive to
operate. Gas lighting for streets gave way to low pressure sodium and high pressure mercury
lighting in 1930s and the development of the electric lighting in 19th century replaced gas lighting in
homes. Later with the invention of fluorescent lamps and Compact fluorescent lamps (CFLs),