Highly-Directional, Highly-Efficient Solution-Processed Light-Emitting Diodes of All-Face-Down Oriented Colloidal
Hamed Dehghanpour Baruj1, Iklim Bozkaya1, Betul Canimkurbey1,2
1Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, 06800, Turkey.
Small (Weinheim an Der Bergstrasse, Germany)
|April 6, 2023
Summary
Colloidal quantum well light-emitting diodes (CQW-LEDs) achieve record 18.1% external quantum efficiency using face-down oriented films. This orientation boosts light outcoupling and performance for solution-processed CQW-LEDs.
Area of Science:
- Materials Science
- Optoelectronics
- Nanotechnology
Background:
- Semiconductor colloidal quantum wells (CQWs) exhibit anisotropic emission due to their optical transition dipole moments (TDMs).
- Achieving high efficiency in CQW-LEDs is crucial for advanced display and lighting technologies.
Purpose of the Study:
- To develop highly efficient, solution-processed CQW-LEDs by controlling the orientation of CQWs.
- To enhance light outcoupling efficiency and overall device performance through controlled self-assembly.
Main Methods:
- Fabrication of CQW-LEDs using a single, all-face-down oriented self-assembled monolayer (SAM) film of CQWs.
- Characterization of the ensemble emission, outcoupling efficiency, external quantum efficiency (EQE), brightness, operational lifetime, and turn-on voltage.
Main Results:
- Achieved a supreme in-plane TDM orientation of 92% in the ensemble emission.
- Enhanced light outcoupling efficiency from 22% to 34% by utilizing face-down oriented emitters.
- Reached a record external quantum efficiency of 18.1% for solution-processed CQW-LEDs.
- Demonstrated high brightness (19,800 cd m⁻²), long operational lifetime (247 h at 100 cd m⁻²), stable deep-red emission (651 nm), and low turn-on voltage (1.7 eV).
Conclusions:
- The oriented self-assembly of CQWs in a SAM film is an effective strategy to improve outcoupling and external quantum efficiencies in CQW-LEDs.
- This architecture enables high-performance, solution-processed CQW-LEDs competitive with state-of-the-art devices.
- The findings pave the way for next-generation solution-processed optoelectronic devices.
