Synthesis and characterization of the fluorinated thieno[3,4-c]pyrrole-4,6-dione-based donor-acceptor polymers for organic solar cells

摘要

A new wide bandgap polymer (PC8TPD-F) has been synthesized via the Stille cross-coupling reaction between fluorine-substituted thieno[3,4-c]pyrrole-4,6-dione (TPD) and 4,8-bis(5-hexylthiophen-2-yl)benzo [1,2-b:4,5-b] dithiophene (BDTT). For structural comparison, the nonfluorinated TPD-based BDTT polymer (PC8TPD) was also synthesized with the same polymerization. The number average molecular weights (Mn) of PC8TPD and PC8TPD-F were found to be 47,000 g/mol (D = 2.1) and 52,000 g/mol (D = 1.8) respectively. The HOMO levels of PC8TPD and PC8TPD-F were determined to be -5.56 and-5.65 eV respectively. The inclusion of the fluorinated TPD unit lowers the polymer's HOMO level. The SCLC mobilities of PC8TPD and PC8TPD-F were determined to be 1.5 x 10(-4) and 2.1 x 10(-4) cm(2)/V respectively. Polymer solar cell devices prepared with PC8TPD and PC8TPD-F as their active layers were found to exhibit power conversion efficiencies of 4.26% and 6.80% with open circuit voltages of 0.90 V and 0.95 V respectively.