Hydrogen bonding in bulk heterojunction solar cells: a case study.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) offer a promising alternative to conventional photovoltaics.
• Molecular design is crucial for optimizing charge transport and morphology in OSCs.
• Dithienothiophene derivatives are effective building blocks for organic semiconductors.

Purpose of the Study:

• To synthesize and characterize small molecules based on dithienothiophene with varying terminal groups (octyl cyanoacetate and octyl cyanoacetamide).
• To investigate the impact of intermolecular hydrogen bonding, introduced by the amide group, on the active layer morphology and photovoltaic performance of bulk heterojunction solar cells.
• To compare the performance of a novel amide-containing fullerene acceptor with conventional fullerene acceptors.

Main Methods:

• Chemical synthesis of small molecules and a novel methanofullerene derivative.
• Fabrication and characterization of bulk heterojunction solar cells.
• Analysis of active layer morphology using techniques sensitive to molecular packing and intermolecular interactions.
• Photovoltaic performance testing under simulated solar illumination.

Main Results:

• Successful synthesis of dithienothiophene-based small molecules with distinct terminal units.
• The molecule with the amide group exhibited intermolecular hydrogen bonding, influencing thin-film morphology.
• Comparison revealed differences in photovoltaic properties and morphology between the two small molecules and fullerene acceptors.

Conclusions:

• Intermolecular hydrogen bonding significantly affects the active layer morphology in organic solar cells.
• The designed amide-containing small molecules show potential for use in bulk heterojunction solar cells.
• Novel amide-functionalized fullerene acceptors warrant further investigation for improved device performance.