3D Volatile Solid Additives: Enhancing Molecular Crystallinity and Prolonging Exciton Lifetime for Binary Organic...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Controlling active layer morphology is crucial for organic solar cell (OSC) performance.
• Three-dimensional (3D) volatile solid additives offer a promising, yet underexplored, approach for morphology control.
• Understanding the working mechanisms of these additives is essential for further advancements.

Purpose of the Study:

• To introduce and investigate two novel 3D volatile solid additives: 2-bromobiphenyl (BB) and 2,2′-dibromobiphenyl (DBB).
• To elucidate the mechanisms by which these additives influence the active layer morphology and performance of OSCs.
• To demonstrate the universality and potential of these additives in various OSC systems.

Main Methods:

• Synthesis and application of BB and DBB as 3D volatile solid additives in OSCs.
• Characterization of active layer morphology, including molecular packing and phase separation, using techniques like thermal annealing.
• Device fabrication and performance testing of OSCs incorporating the additives, measuring power conversion efficiency (PCE).

Main Results:

• BB and DBB effectively induced molecular packing and facilitated self-assembly of donor and acceptor materials.
• Optimized active layers exhibited enhanced molecular crystallinity and favorable phase separation.
• OSCs using BB and DBB achieved PCEs of 18.07% and 19.03%, respectively, outperforming devices without additives (17.06%).
• A DBB-treated OSC achieved a record PCE of 19.57% with a [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) hole transport layer.
• DBB demonstrated broad applicability in PM6:Y6 and D18:Y6 systems.

Conclusions:

• 3D volatile solid additives like BB and DBB are effective in controlling OSC active layer morphology.
• These additives enhance molecular packing, crystallinity, and phase separation, leading to improved device performance.
• DBB shows significant potential as a universal additive for high-efficiency organic solar cells.