Efficient Solution Processable Polymer Solar Cells Using Newly Designed and Synthesized Fullerene Derivatives

Abstract

Two modified PC60BM and PC70BM fullerene derivates denoted as C60DAM and C70DAM, respectively, were synthesized and characterized. Through the structural modification, the lowest unoccupied molecular orbital (LUMO) energy level of these fullerene derivatives can be raised as much as 0.15 eV with respect to that of their parent fullerene derivatives, which is possibly ascribed to the electron-donating nature of their substituted moiety. Bulk heterojunction (BHJ) polymer solar cells (PSCs) fabricated with poly(3-hexylthiophene) (P3HT) as electron donor and either C60DAM or C70DAM as electron acceptor showed both higher open-circuit voltage (Voc) and short-circuit current (Jsc), resulting in enhanced power conversion efficiency (PCE) (3.23% for P3HT:C60DAM and 4.45% for P3HT:C70DAM) as compared to corresponding PC60BM. The enhanced Jsc and higher Voc values have been ascribed to the stronger absorption in the visible region and increase in LUMO level of the modified fullerene derivatives compared to their pr...