Cu(I) Halide Complexes with Benzo[b]thiophenyl Triphosphine for Highly Emissive TADF-OLEDs

Area of Science:

• Materials Science
• Inorganic Chemistry
• Photophysics

Background:

• Research interest in luminescent Cu(I) halide complexes with rigid phosphine ligands.
• Unreported systems using fused-heterocyclic triphosphine ligands.
• Challenge in achieving high quantum efficiency and short decay lifetimes simultaneously.

Purpose of the Study:

• Synthesize novel mononuclear copper(I) halide complexes with benzo[b]thiophene-based triphosphine ligands.
• Characterize their structures and photophysical properties.
• Evaluate their potential for organic light-emitting devices (OLEDs).

Main Methods:

• Synthesis of a rigid triphosphine ligand incorporating benzo[b]thiophene units.
• Preparation of three mononuclear copper(I) halide complexes (CuX(L1)).
• Structural and photophysical characterization (spectroscopy, lifetime measurements).
• Fabrication and testing of vacuum-deposited OLEDs.

Main Results:

• Successful synthesis and characterization of CuI(L1) (1), CuBr(L1) (2), and CuCl(L1) (3).
• Complexes 1-3 exhibit intense yellow-green to yellow-orange delayed fluorescence (557-586 nm) with high quantum yields (up to 0.58) and short lifetimes (3.5-6.9 μs).
• OLEDs using complex 1 show high-purity yellow electroluminescence with a maximum external quantum efficiency (EQE) of 11.77%.

Conclusions:

• The benzo[b]thiophene moiety enhances photoluminescence quantum yield and allows color tuning.
• Complex 1 demonstrates excellent performance for yellow OLED applications.
• These findings present a new class of efficient emitters for optoelectronic devices.