O-B(F)←N Functionalized Copolymers with Delayed Fluorescence and P-Type Semiconducting Characteristics

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Conjugated polymers with both delayed fluorescence and photovoltaic properties are rare due to conflicting molecular design requirements.
• Achieving simultaneous delayed fluorescence and efficient charge generation in organic semiconductors remains a significant challenge.

Purpose of the Study:

• To design and synthesize novel conjugated polymers that exhibit both delayed fluorescence and photovoltaic responses.
• To investigate the structure-property relationships of these new polymers for potential applications in organic electronics.

Main Methods:

• Design of a novel O-B(F)←N functionalized fused unit (M) with specific photophysical properties.
• Copolymerization of the M unit with benzodithiophene (BDT) derivatives to create new polymer backbones.
• Characterization of the polymers' photophysical properties, including delayed fluorescence lifetime (τD) and singlet-triplet energy gap (ΔEST).
• Evaluation of the polymers' semiconductor characteristics, such as hole mobility.
• Fabrication and testing of organic photovoltaic (OPV) devices using the synthesized polymers as donors.

Main Results:

• A novel O-B(F)←N functionalized unit was designed, exhibiting delayed fluorescence (τD = 0.75 µs) and a small singlet-triplet energy gap (ΔEST = 0.23 eV).
• Copolymers incorporating this unit demonstrated sustained delayed fluorescence (τD = 0.4-0.5 µs) and p-type semiconductor behavior with hole mobilities of 10⁻⁶–10⁻⁵ cm²/Vs.
• Organic photovoltaic devices fabricated with these polymers achieved a preliminary power conversion efficiency of 5.05%.

Conclusions:

• The introduction of O-B(F)←N functional groups into conjugated polymer backbones is an effective strategy for integrating delayed fluorescence and photovoltaic properties.
• These novel polymers show significant potential for advanced organic electronic applications, particularly in energy conversion and light-emitting devices.
• This study provides a new molecular design approach for multifunctional conjugated polymers.