UPCOMINGEVENTS

INTRODUCINGour NEWEX-CO

ACADEMICARTICLE

OLEDWHOLE YEAR

TIMELINEFLEXIBLE DISPLAY

EXOTHERMIC

FOREWORD

Exothermic is defined as a chemical process that releases heat. Uniting all Members as a harmonic family with our passion and enthusiasm disseminated, is one of our focuses this year. Though it may sound simple, yet, it is really an enormous challenge.

2012 - 2013, for the sake of the double-cohort entries, there is a dramatic raise in Members. Although this is a special year for us, we will still strive our best to overcome the challenge, by consociating 12 of us as a whole and illuminating exothemically. In University, apart from study, there are still thousands of choices for having fun. This year, numerous functions from different aspects has already been well-prepared by the Chemistry Society, SS , HKUSU, exclusively for you.

Without your encouragement and participation, our session will never succeed.

Please continue supporting Exothermic, the 15th cabinet of Chemistry Society, SS, HKUSU!

Chemistry Society, SS, HKUSUSession 2012 - 2013, Exothermic

EVENTS

Inauguration Ceremony24th January Start-of-Semester

Party30th January

2013

Photo Day21st February Firm Visit I

12th March

Welfare Week I25th - 28th February Joint-University

ActivitiesMid March - Mid April

Super-Pass Dinner12th April

Registration Day andOrientation Series

AugustOld Book FairMid September

Welfare Week IIMid SeptemberCommencement Dinner

Mid September

Firm Visit IIEarly OctoberCareer Talk

Mid October

SocialWelfare

AcademicOrientation

INTRODUCTIONS OF EX-CO

NG Kwok WaiCHAIRMAN3 - Year Curriculum

HO Oi YanINTERAL-VICE CHAIRMAN3 - Year Curriculum

CHANVITITKUL PhasuraEXTERAL-VICE CHAIRMAN3 - Year Curriculum

IP Chi WaiGENERAL SECRETARY4 - Year Curriculum

KWOK Hing ManFINANCIAL SECRETARY3 - Year Curriculum

LAU Ka LapACADEMIC SECRETARY4 - Year Curriculum

INTRODUCTIONS OF EX-CO

LEONG Man KwanMARKETING SECRETARY4 - Year Curriculum

LEE Kin LokPUBLICATION AND PUBLICITY SECRETARY

4 - Year Curriculum

NG Ping HonWELFARE SECRETARY3 - Year Curriculum

TAM Ka KiPUBLICATION AND PUBLICITY SECRETARY

3 - Year Curriculum

LOK Hou UnSOCIAL AND SPORTS SECRETARY

4 - Year Curriculum

LEE Chun LokSOCIAL AND SPORTS SECRETARY

4 - Year Curriculum

ACADEMIC

(Fig. 1)Basic structure of an OLED cell

(Fig. 2) Working principle of an OLED

Based on smaller molecules:- First developed by Dr. Ching W. Tang in 1987.- Commonly use molecules in the ETL : i. Organometallic complexes EXAMPLE : tris(8-hydroxyquinolinato)aluminum - Used for emitting different colours of visible light ii. Fluorescent and phosphorescent dyes and conjugated dendrimers are used as emissive layer later on.

electrons. In order to improve device performance, an electron-transport layer (ETL) will also be used to enhance the charge balance. Finally, low work function metals like calcium and lithium are used as the cathode. The cathode is normally coated with aluminum to avoid degradation due to its high metal reactivity.

Introduction:

Recently, there were various news on the use of OLED (Organic Light-Emitting Diode) to manu-facture screens of smart phones. It seems that foldable smart phones can be developed if the technology of OLED is used in place of LCD (Liquid Crystal Display). In this article, basic structure of OLED, working principle of OLED, important chemicals involved and also the applications of OLED will be discussed.

Basic Structure of OLED:

A typical OLED consists of two or more organic layers sandwiched between two electrodes. Fig. 1 depicts a basic structure of OLED cell as an example. The first layer deposited on a transparent sub-strate (glass or plastic) is a hole-injecting anode. The anode is gen-erally made of indium tin oxide (ITO). In a basic bilayer OLED cell, one organic layer would be a hole-transport layer (HTL) and the other layer in contact with the cathode would be used as emissive layer for light emission. The interface between two layers provides an efficient site for the recombination of the injected holes and

Working principle:

When a voltage is applied across the OLED, electrons will be inject-ed from the cathode into the lowest unoccupied molecular orbitals (LUMO) of the ETL and move towards the anode(+) while holes will injected from the anode into the highest occupied molecular orbitals (HOMO) of the HTL and will move in opposite direction. Holes and electrons will then collide within the emissive layer and recombine to form excitons which are the bound states of electrons and holes. The collisions would happen close to the emissive layer due to the higher mobility of holes. The relaxation of the energy levels of the excitons causes the emission of photons with specific wavelength, hence producing visible light.

Important chemicals involved:

Generally, there are two families of OLEDs, i.e. one of them is based on smaller molecules and the other uses polymers and so-called ‘’ PLED’’ (polymer light-emitting diodes).

Article: Lau Ka Lap

ACADEMIC

References:

LED ESL (light emitting diode energy saving lamp). Accessed on 9th of November,2012. OLED Working principle. Retrieved from http://www.ledesl.com/01-12-2009/oled-working-principle.htmlSAMSUNG (2005, 22 March). Samsung Asserts Mobile Industry Leadership with Six Com-pelling Solutions in Memory, System Logic and Display. SAMSUNG.Tang, C.; VanSlyke, S. (1987). Organic electroluminescent diodes. Applied Physics Letters. Volume 51. Issue 12, Page 913.Wikipedia. Accessed on 10th of November, 2012. OLED. Retrieved from http://en.wikipedia.org/wiki/O-LED#cite_note-ApplPhy87-18

Prachi, P. Accessed on 7th of November, 2012. Organic LEDs Shine Invisibly. Retrieved from http://www.technologyreview.com/news/407241/organic-leds-shine-invisibly/

Ho, Y.; Lee, S. (2008). Effect of Hole Injection Layer/Hole Transport Layer Polymer and Device Structure on the Properties of White OLED. Journal of Nanoscience and Nanotech-nology. Volume 8. Issue 10, Page 4916-22.

Link of the news report:

http://hk.news.yahoo.com/%E4%B8%89%E6%98%9F%E6%93%AC%E6%98%8E%E5%B9%B4%E9%87%8F%E7%94%A2%E5%8F%AF%E6%91%BA%E8%86%A0%E5%B1%8F%E5%B9%95-222939348.htmlPhotos:

http://www.wirelessdesignonline.com/doc.mvc/OLEDs-Open-up-New-Options-in-Display-Technolo-0002http://www.maximumpc.com/article/features/white_paper_oled_screenshttp://www.flickr.com/photos/mshades/2058600503/http://www.commonchemistry.org/ChemicalDetail.aspx?ref=2085-33-8http://www.rsc.org/Membership/Networking/InterestGroups/OrganicDivision/organic-chemistry-case-studies/organic-chemistry-plastic-electronics.asphttp://www.sunatech.com.cn/productshow.asp?selid=160http://ces.cnet.com/8301-34435_1-57563058/eyes-on-samsungs-youm-flexible-display-tech-at-ces-2013/

(Fig. 3) Tris(8-hydroxyquinolinato)aluminum

Based on polymers :EXAMPLE : i. Derivatives of poly(p-phenylene vinylene) ii. Polyfluorene- The colour of light emitted is determined by the side chains on the polymer backbone.

(Fig. 4a) Poly(p-phenylene vinylene)

(Fig. 4b) Polyfluorene

Phosphorescent materials:- Added to the emissive layers as a dopant emitter. EXAMPLE : i. Iridium complexes such as Ir(ppy)3 - Added into polymers like poly(N-vinylcarbazole) as emissive layer to improve the internal efficiency of light emission of the devices.

(Fig. 5) Ir(ppy)3

(Fig. 6a) (Fig. 6b)

Application of OLED:

1. To produce invisible infrared light for military applications in early days.EXAMPLE : i. Soldiers can use this kind of diodes to communicate at night without being detected by opponents.2. To be used in flat-panel displays and lighting applications nowadays.REASON : Because of its thinness. - Due to the presence of organic semiconductor layers in OLED instead of the bulky alignment layers and spacers in LCD. EXAMPLE : i. In televisions and computers. (Included the largest televisions in the world in 2008 launched by the Samsung with 4.3mm thin) ii. Bending smart phones (Investigation is currently in progress, will be launched soon by the Samsung)

Chemistry Society, SS, HKUSUSession 2012 ~ 2013

NewsletterVolume I

Publisher: Chemistry Society, SS, HKUSUEditor: Tam Ka Ki Kristy

Art Director: Lee Kin Lok Lucas

Website: http://www.chemsoc.hkusu.hku.hk/Email: chemsoc@hku.hk