Conjugation-Broken Dimer Acceptors Enable High-Efficiency, Stable, and Flexibility-Robust Organic Solar Cells.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Dimer acceptors in organic solar cells (OSCs) offer advantages like defined structures and reproducibility.
• High glass transition temperatures (Tg) of dimer acceptors contribute to optimal morphology and device stability.
• Current dimer acceptors often use conjugated linkers to achieve high power conversion efficiencies (PCEs).

Purpose of the Study:

• To synthesize and investigate a new series of dimer acceptors with flexible alkyl linkers.
• To evaluate the impact of these flexible conjugation-broken linkers (FCBLs) on PCE, device stability, and flexibility.
• To establish the relationship between linker length and OSC performance and stability.

Main Methods:

• Synthesis of novel dimer acceptors (T1, T4, T6, T12) with varying flexible alkyl linkers.
• Fabrication and testing of OSC devices blended with PM6.
• Molecular dynamics simulations and density functional theory (DFT) calculations.

Main Results:

• The T6-based device achieved a PCE of 17.09%, comparable to the conjugated T0 device (17.12%).
• FCBLs were found to promote intermolecular electronic couplings, maintaining good electron mobilities.
• The T6 device demonstrated significantly improved long-term stability (T80 = 1427 h) compared to the T0 device (T80 = 350 h).

Conclusions:

• Flexible conjugation-broken linkers are effective in designing high-performance and stable dimer acceptors for OSCs.
• The length of flexible alkyl linkers directly influences the performance and stability of OSCs.
• This study provides insights for developing next-generation efficient and durable organic solar cell materials.