Dimeric Giant Molecule Acceptors Featuring N-type Linker: Enhancing Intramolecular Coupling for High-Performance...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Giant molecular acceptors (GMAs) enhance polymer solar cell (PSC) stability by increasing glass transition temperature (T_g).
• Optimizing GMA chemical structure is crucial for improving device performance.
• Previous GMAs often used p-type linkers; exploring n-type linkers offers new design possibilities.

Purpose of the Study:

• To investigate the use of an n-type benzothiadiazole linker to dimerize small molecule acceptors (SMAs).
• To synthesize and characterize a novel GMA, BT-DL, and compare its properties to a benzene-linked analog (B-DL).
• To evaluate the performance and stability of PSCs utilizing BT-DL as the acceptor material.

Main Methods:

• Synthesized BT-DL via a Knoevenagel condensation using an n-type benzothiadiazole linker.
• Fabricated PSC devices using BT-DL and B-DL as acceptor materials blended with polymer donors.
• Characterized material properties including intramolecular coupling, absorption, crystallinity, and electron mobility.
• Tested device power conversion efficiency (PCE) and long-term operational stability under thermal stress.

Main Results:

• BT-DL exhibited stronger intramolecular super-exchange coupling compared to B-DL.
• BT-DL showed enhanced film absorption, redshifted absorption spectrum, larger crystalline coherence, and higher electron mobility.
• PSCs with BT-DL achieved a significantly higher PCE of 18.49% compared to 9.17% for B-DL.
• The BT-DL based device retained over 90% of its initial efficiency after 1000 hours at 90°C.

Conclusions:

• The n-type benzothiadiazole linker effectively enhances GMA properties for improved photovoltaic performance.
• BT-DL offers a promising strategy for developing highly efficient and stable PSCs.
• This approach provides a cost-effective method for synthesizing advanced GMAs for durable photovoltaic technologies.