Gate Controlled Excitonic Emission in Quantum Dot Thin Films

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Charged trions in colloidal quantum dot (QD) thin films reduce luminescence quantum efficiency due to nonradiative recombination.
• Controlling charged trion formation is crucial for fundamental understanding and optimizing QD performance.

Purpose of the Study:

• To investigate the effect of background charge on luminescence efficiency and lifetime in QD thin films.
• To demonstrate a device for reversible control of charged trion concentration and luminescence.

Main Methods:

• Fabrication of a metal-oxide-semiconductor capacitor using CdSe/CdS QD thin films.
• Applying gate voltage to control the concentration ratio of charged and neutral quasiparticles.
• Performing simultaneous steady-state and time-resolved photoluminescence measurements.

Main Results:

• Photoluminescence intensity was modulated by up to two orders of magnitude.
• Effective luminescence lifetime showed a corresponding change with gate voltage.
• Chip-scale modulation of brightness was achieved, effectively turning photoluminescence on and off.

Conclusions:

• A QD-based metal-oxide-semiconductor capacitor enables effective control over luminescence efficiency and lifetime.
• This voltage-controlled modulation highlights potential for applications in advanced electrochromic devices.