All Inorganic Colloidal Quantum Dot LED with Metal Oxide Charge Transport Layers

Student: Haider Salman

Degree: M.S., December 2015

Major Professor: Dr. Omar Manasreh

Research Area(s):

Nanoscience & Engineering

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Background/Relevance

  • Highly efficient quantum dots LED have promising applications in display technology due to narrow emission and tunable color.
  • Research is being conducted to investigate the mechanism of these devices since their physics is not yet understood.

Innovation

  • Low cost advantage of the solution processed layers deposited by spin coating compared with the organic material LEDs.
  • Synthesis of colloidal quantum dots can result in much higher monodispersed colloid than those obtained by epitaxial growth.
  • Choosing the materials of the layers that form the device is a key principle in the device fabrication.

Approach

  • Use sol-gel procedure to synthesize the solution processed layers of the LED.
  • Deposit the LED layers on ITO slides using spin coater.
  • CdSe/ZnS, ZnO, and NiO are used as the emissive, electron, and hole injection layer, respectively.
  • MoO3 was also prepared as an alternative hole transport layer.
  • Deposit 100 nm aluminum cathode using ebeam am evaporator

Key Results

  • Synthesized materials were characterized using PL, absorbance, and Raman Spectroscopy. XRD and XPS were used to investigate the crystallinity of the deposited thin films.
  • I-V characteristics of the device showed a turn-on voltage at 4 V and a maximum current density at 9 V.
  • NiO carrier concentration was investigated by fabricating Schottky diode made of Al and NiO thin film.

Conclusions

  • Using NiO as the P-type HTL represents a good option due to its electrochemical stability, low cost, and easy synthesis procedure.
  • The obtained efficiency is still low and the device turn-on voltage is still high.

Future Work

  • More research is required to increase the efficiency and lower the turn-on voltage of the device.
  • More investigation to understand the physics of the device working principles especially the role of Auger recombination and Forster resonance.