Precursor engineering towards orange- and red-emissive carbon dots for LEDs with tunable emission colors

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Carbon dots (CDs) show promise for optoelectronic devices.
• Understanding the source of CD structural and optical diversity is limited.

Purpose of the Study:

• Investigate how precursor molecular structure influences carbon dot properties.
• Explore the application of synthesized CDs in light-emitting diodes (LEDs).

Main Methods:

• Synthesized carbon dots from two structurally similar benzenoid acids: 9-oxo-9H-fluorene-2,7-dicarboxylic acid (FR) and 4,4'-biphenyl dicarboxylic acid (BP).
• Characterized the optical properties (emission color, quantum yield) of the synthesized CDs.
• Fabricated and tested LEDs using a blend of poly(N-vinyl carbazole) (PVK) and CDs.
• Employed combined experimental and theoretical approaches to analyze structure-property relationships.

Main Results:

• FR-derived CDs emitted orange light (43.1% quantum yield), while BP-derived CDs emitted red light (30.9% quantum yield).
• LEDs fabricated with CDs-FR and CDs-BP exhibited cyan and yellow light, respectively, with moderate turn-on voltages and luminance.
• Observed differences in optoelectronic performance were linked to energy-level alignment variations between CDs and PVK.

Conclusions:

• The structural variations in precursors directly lead to the diverse optical and optoelectronic properties of carbon dots.
• This research provides a framework for rationally selecting precursors to engineer CDs with specific optical and optoelectronic functionalities.
• The findings contribute to the development of tailored carbon dots for advanced LED applications.