Dye-Containing Polymers with π-Extened Diketopyrropyrrole Derivatives for Semi-Transparent Organic Photovoltaics

Area of Science:

• Materials Science
• Organic Chemistry
• Polymer Science

Background:

• Diketopyrrolopyrrole (DPP) derivatives are crucial for developing narrow band gap organic dyes.
• Extending π-conjugation in DPP structures can enhance optoelectronic properties.
• Benzo[1,2-b:4,5-b']dithiophene (BDT) units are widely used to tune the electronic properties of organic semiconductors.

Purpose of the Study:

• To synthesize novel narrow band gap dye-containing polymers (P1 and P2) based on a π-extended DPP core.
• To investigate the structure-property relationships of these polymers for applications in organic electronics.
• To evaluate the performance of the synthesized polymers in organic field-effect transistors (OFETs) and bulk heterojunction (BHJ) solar cells.

Main Methods:

• Synthesis of a π-extended DPP (EDPP-OT-BrPh) via Ru(III)-catalyzed C-H and N-H activation.
• Polymerization of EDPP-OT-BrPh with BDT derivatives (P1 and P2) incorporating 2-octylthiophene side chains for improved solubility.
• Fabrication and characterization of OFETs and BHJ solar cells using the synthesized polymers.

Main Results:

• The π-extended DPP exhibited a high photoluminescence quantum yield (ϕem=0.84) and a small HOMO-LUMO gap (Eg=1.69 eV).
• Polymers P1 and P2 demonstrated good carrier mobility (approximately 10⁻⁵ cm²/Vs) in OFET devices.
• BHJ solar cells fabricated with P1 and P2 achieved a power conversion efficiency (PCE) of 1.0% with an average transmittance (AVTs) of ~60%.

Conclusions:

• The synthesized narrow band gap polymers show potential for use in organic electronic devices.
• The strategy of extending π-conjugation and incorporating solubilizing side chains is effective for developing high-performance organic semiconductor dyes.
• Further optimization could lead to improved efficiencies in OFETs and solar cells.