High External Quantum Efficiency Light-Emitting Diodes Enabled by Advanced Heterostructures of Type-II Nanoplatelets

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Colloidal quantum wells (CQWs), or nanoplatelets (NPLs), are promising for photonic applications like lasers and LEDs.
• Type-I NPL-LEDs are well-developed, but type-II NPLs remain underexploited for LED applications, despite potential for enhanced optical properties.

Purpose of the Study:

• To develop and investigate novel multi-crowned type-II NPLs (CdSe/CdTe/CdSe).
• To compare the optical properties of these advanced NPLs with traditional core/crown counterparts.
• To demonstrate their application in high-performance NPL-LEDs.

Main Methods:

• Synthesis of CdSe/CdTe/CdSe multi-crowned type-II NPLs.
• Optical characterization including quantum yield (QY) and fluorescence lifetime measurements.
• Electron and hole wave function modeling for theoretical analysis.
• Fabrication and testing of NPL-LED devices.

Main Results:

• The multi-crowned type-II NPLs exhibit a high QY of 83% and a long fluorescence lifetime of 73.3 ns, attributed to dual type-II transition channels.
• Computational studies revealed improved hole wave function distribution and electron delocalization.
• NPL-LEDs fabricated with these NPLs achieved a record external quantum efficiency (EQE) of 7.83% for type-II NPL-LEDs.

Conclusions:

• The developed multi-crowned type-II NPLs offer superior optical properties compared to traditional type-II NPLs.
• These findings demonstrate the potential of advanced NPL heterostructures for high-performance LEDs and lasers.
• This work encourages further design of NPL heterostructures for next-generation photonic devices.