| 초록 |
While most of high-efficiency polymer solar cells (PSCs) are made of bulk hetrojunction (BHJ) blends of conjugated polymers and fullerene derivatives, they inhere a significant morphological instability issue against the mechanical and thermal stress. Herein, we developed an architecturally new type of compatibilizer, poly(3-hexylthiophene)-graft-poly(2-vinylpyridine) (P3HT-g-P2VP) that effectively modifies the sharp interface of a BHJ layer comprised of a P3HT donor and various fullerene acceptors, resulting in a dramatic enhancement of mechanical and thermal stabilities. We directly measured the mechanical properties of active layer thin films without a supporting substrate for the first time by floating a thin film on water, and the enhancement of mechanical stability without loss of the electronic functions of PSCs were successfully demonstrated. Supramolecular interactions between the P2VP of the P3HT-g-P2VP polymers and the fullerenes generated their universal use as compatibilizers regardless of the type of fullerene acceptors, including mono- and bis-adduct fullerenes, while maintaining their high device efficiency. Most importantly, the P3HT-g-P2VP copolymer had better compatibilizing efficiency than linear type P3HT-b-P2VP with much enhanced mechanical and thermal stabilities. The graft architecture promotes preferential segregation at the interface, resulting in broader interfacial width and lower interfacial tension as simulated by molecular dynamics model. Both the experiments and computational simulations consistently supported that the graft architecture is beneficial for the design of compatiblizers for enhancing the stabilities of highly efficient PSCs. |
