Structurally Locked A-D-A-Type Medium-Bandgap-Small-Molecule Donors for Low-Cost and High-Efficiency...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• High-performance organic solar cells (OSCs) often rely on complex polymer donors or fused-ring small-molecule donors (SMDs), hindering their efficiency and scalability.
• Current synthetic routes for advanced SMDs are frequently multi-step and complex, limiting their practical application and cost-effectiveness.

Purpose of the Study:

• To design and synthesize simple, medium-bandgap A-D-A type SMDs with facile synthetic routes.
• To investigate the impact of π-linker modifications and intramolecular noncovalent interactions on molecular planarity and performance in OSCs.
• To achieve high power conversion efficiencies (PCEs) in nonhalogen solvent-processed all-small-molecule OSCs (ASM-OSCs).

Main Methods:

• Synthesized two A-D-A type SMDs, AW-01 and AW-02, using a four-step route involving direct C-H arylation and Knoevenagel condensation.
• Employed an intramolecular noncovalent interaction strategy to enhance molecular planarity, utilizing O···S and O···H interactions in AW-02.
• Fabricated nonhalogen solvent-processed ASM-OSCs using the synthesized SMDs paired with a Y6 acceptor and characterized their photovoltaic performance.

Main Results:

• AW-02, featuring an ethylenedioxythiophene linker and enhanced noncovalent interactions, exhibited rigidification and J-aggregation, leading to complementary absorption with the Y6 acceptor.
• ASM-OSCs based on AW-02/Y6 achieved a high PCE of 15.11%, significantly outperforming AW-01 (7.49%).
• The superior performance of AW-02 was attributed to enhanced charge transport, balanced mobilities, reduced radiative energy losses, and suppressed trap-assisted recombination.

Conclusions:

• Developed a promising strategy for creating simple, low-cost, and highly efficient SMDs for scalable ASM-OSCs.
• AW-02 demonstrates potential as a viable alternative to high-efficiency polymer donors and complex fused SMDs.
• The study highlights the importance of molecular design, including noncovalent interactions, for optimizing OSC performance.