Simple-Structured NIR-Absorbing Small-Molecule Acceptors with a Thiazolothiazole Core: Multiple Noncovalent...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Developing efficient near-infrared (NIR) absorbing small-molecule acceptors (SMAs) is crucial for advancing organic solar cells (OSCs).
• Existing SMAs often lack simple structures or sufficient NIR absorption for commercial viability.
• Tailoring molecular design is key to enhancing photovoltaic performance in OSCs.

Purpose of the Study:

• To design and synthesize novel, simple-structured NIR-absorbing SMAs.
• To investigate the impact of specific side chains and noncovalent interactions on molecular conformation and optical properties.
• To evaluate the photovoltaic performance of these SMAs in solution-processed OSCs.

Main Methods:

• Synthesis of two novel thiazolothiazole-centered SMAs (TTz3 and TTz4) featuring alkoxy/alkylthio side chains.
• Characterization of molecular structure and confirmation of noncovalent conformational locks (S···N, S···O, S···S).
• Fabrication and testing of organic solar cells using the synthesized SMAs with a J71 donor.

Main Results:

• The novel SMAs exhibited extended planar configurations and red-shifted NIR absorption due to conformational locks.
• TTz3-based organic solar cells achieved a high power conversion efficiency of 8.76%.
• A low energy loss of 0.57 eV was recorded for the TTz3-based devices, indicating high efficiency.

Conclusions:

• The developed simple-structured SMAs demonstrate efficient NIR absorption and high photovoltaic performance.
• The incorporation of specific side chains and noncovalent locks effectively enhances molecular planarity and optical properties.
• These findings present a significant advancement for NIR-absorbing SMAs with potential applications in semitransparent organic solar cells.