Research Powerpoint

Brandon Hart, Department of Chemical Engineering Mentor: Omar Manasreh, Ph.D., Department of Electrical Engineering

Graduate Student Mentor: Ramesh Vasan, Department of Electrical Engineering

7th Annual FEP Honors Research Symposium

April 18th, 2015

HART 7TH ANNUAL FEP HONORS RESEARCH SYMPOSIUM 1

Development of II-VI All-Inorganic Colloidal Quantum Dot Light Emitting Devices


[1.]

[2.]

Technology


[3.] [4.]

LED Displays


Semiconductor- a material that has intermediate conductivity between a conductor and an insulator

HART 7TH ANNUAL FEP HONORS RESEARCH SYMPOSIUM


[5.]

Doping of a semiconductor

Doping- the process in which impurities are introduced to manipulate its electric properties.


P-N Junction

P-N junction- the location where electrons recombine and release photons.

[6.]


Emissive Layer

Emissive Layer- layer of nanocrystals that transports electrons from the cathode to the anode.


Electroluminescence

Electroluminescence- photon (light particle)

emitting process.

[7.]


[8.]

Quantum Dot

Quantum Dot- A nanoscale particle of semiconducting material that can be embedded in cells or organisms for various purposes.


Quantum Dot Band Gap

[9.]

• Quantum Dot Band Gap- Energy of the photon emitted.

• The color of the quantum dot depends on the size.


[10.]

Quantum Dot Emissive Layer


[10.]

Advantages of Quantum Dot LEDs


Advantages of Quantum Dot LEDs

(1) Narrower emission bandwidth = more saturated and

purer color than OLEDs.

(2) Adjustable emission colors through size and shape of

quantum dot.

(3) Cost of QLEDs are much lower than OLEDs.


[10.]

Current progression of LEDs


Current progression of LEDs

Quantum Dot LED Issues: • High turn-on voltages• Low device efficiency in practicable brightness

region• Inefficient carrier injection


Research Objectives

• Understand the working of QLED• Understand the current carrier injection method• Improve the carrier injection capabilities within the

semiconductor device• Develop a new carrier injection technique• Test new carrier injection technique to determine

improvements


Carrier Injection

Carrier Injection- method for fabricating nanocrystal quantum dot emissive layer.


Synthesis of Quantum Dots


Spin Coating Technique

[11.]


No Voltage

With Voltage

Testing of QDLEDs


Results

0 1 2 3 4 5 6 7 8 90

25

50

75

100

125

150

175

Cur

rent

Den

sity

(mA

/cm2 )

Voltage (V)

CdSe/ZnS QD LEDEmission at ~520 nm

Anode/HTL/QD/ETL/CathodeITO/NiO/CdSe@ZnS/ZnO/Al


In conclusion, we were able to create quantum dots in a lab and apply them to a light emitting application.

• The semiconductor produced a bright green light with the band gap energy of ~520 nm.

• The new carrier injection method seemed to produce better results than previous methods.

Questions?

Research Powerpoint

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