Intrinsically charge-generating polymers with long-lived free carriers for efficient photon-to-hydrogen conversion

Area of Science:

• Materials Science
• Photocatalysis
• Organic Electronics

Background:

• Single organic semiconductors face challenges with inefficient charge generation due to high exciton binding energy, especially in narrow-bandgap materials absorbing near-infrared (NIR) light.
• Frenkel excitons in organic semiconductors have a high binding energy (approximately 0.5 electron volts), hindering efficient charge separation.

Purpose of the Study:

• To develop a single-component organic photocatalyst capable of NIR photon absorption and simultaneous generation of long-lived free charges.
• To investigate the potential of double-cable polymer nanoparticles for self-sustained photoelectric conversion.

Main Methods:

• Synthesis of as-DCPIC, a double-cable polymer comprising electron-donating PBDB-T backbones and electron-deficient TPDIC side chains.
• Fabrication of nanoparticles (NPs) from the as-DCPIC polymer.
• Characterization using transient absorption spectroscopy and decay kinetics to analyze charge separation and carrier lifetimes.

Main Results:

• As-DCPIC NPs demonstrated NIR photon absorption and efficient generation of long-lived free charges (109 nanoseconds).
• Significantly enhanced hydrogen evolution performance (11.88 mmol/h/g) was observed for as-DCPIC NPs compared to pristine PBDB-T or TPDIC NPs.
• Transient absorption spectroscopy confirmed effective electron-hole separation within the as-DCPIC NPs.

Conclusions:

• Double-cable polymers offer a promising platform for creating efficient single-component organic photocatalysts.
• The developed as-DCPIC NPs effectively generate long-lived reactive charges, paving the way for advanced photocatalytic applications.
• This approach overcomes limitations of intrinsic charge generation in single organic semiconductors.