Polythiophenes with alkylthiophene side chains for efficient polymer solar cells

We synthesized two polythiophene derivatives with alkylthiophene side chains, named PT4T-0F and PT4T-2F. The introduction of alkylthiophene side chains endowed PT4T-0F with more ordered edge-on stacking in film, resulting in higher hole mobility of 0.45 cm2V- 1s- 1 in organic field-effect transistors in comparison to P3HT. Further introducing fluorine atoms, a mainly face-on orientation was achieved for PT4T-2F neat film, which was facilitated to charge transport and collection in polymer solar cells (PSCs). Using F8IC as acceptor, the PSC devices based on PT4T-2F achieved the champion efficiency of 10.48%, owing to the appropriate film morphology with moderate phase separation and favorable face-on molecular orientation. Such efficiency greatly outperformed those of PT4T-0F (2.85%) and P3HT (0.35%) based devices.