20.31% Efficiency Layer-by-Layer Organic Solar Cells Enabled by 3D Side-Chain Topology-Driven Dual-Fiber...

Area of Science:

• Materials Science
• Organic Electronics
• Nanotechnology

Background:

• Constructing stable nanofibrillar networks in organic solar cells (OSCs) is difficult due to the limited interlocking ability of small-molecule acceptors.
• Existing methods struggle to achieve the necessary structural integrity for high-performance devices.

Purpose of the Study:

• To develop a topology-driven strategy for inducing fibrillation in small-molecule acceptors using bulky side chains.
• To investigate the impact of siloxane-terminated side chains on acceptor morphology and device performance in layer-by-layer (LbL) OSCs.

Main Methods:

• Synthesized asymmetric small-molecule acceptors (BTP-2Ph, BTP-3Ph) with varying siloxane-terminated side chains (diphenylmethylsilyl, triphenylsilyl).
• Investigated the morphology and intermolecular interactions using techniques sensitive to nanoscale structure.
• Fabricated and characterized OSC devices using the novel acceptors paired with the D18 donor.

Main Results:

• The triphenylsilyl group in BTP-3Ph induced strong intermolecular interlocking, forming an interconnected acceptor nanofibrillar network.
• This network created an ideal dual-fiber morphology with the D18 donor, surpassing the performance of the L8-BO acceptor.
• The D18/BTP-3Ph device achieved a power conversion efficiency of 20.31%, outperforming L8-BO (19.28%).
• The interlocked framework improved operational stability, retaining 85% of initial efficiency after 650 hours of illumination.

Conclusions:

• Bulky siloxane-terminated side chains can effectively induce fibrillation and create robust acceptor networks in OSCs.
• The topology-driven strategy offers a pathway to enhance both efficiency and stability in organic solar cells.
• This physically interlocked framework provides kinetic stabilization of the optimal morphology, crucial for long-term device operation.