| 초록 |
Medium bandgap polymers have attracted interest for achieving high performance PSCs due to low-lying HOMO energy level and different light absorption region complementary with the absorption region of low bandgap polymer. Hence, the medium bandgap polymer affords high VOC to PSCs and can also be used as a short-wavelength absorber in multi-junction PSCs with low bandgap polymer. We synthesized isoindigo-based medium bandgap conjugated polymer (PI2FT) consisting of isoindigo and difluoro-bithiophene. PI2FT showed the optical bandgap of 1.63 eV and the HOMO energy level of 5.71 eV, respectively. The PSCs fabricated from PI2FT:PCBM blend shows a PCE of 7.9% with a VOC of 1.03 V in conventional device architecture. To the best of our knowledge, the VOC of 1.03 V is among one of the highest ones for PSCs. Therefore, this result clearly demonstrates that PI2FT is a promising material as short-wavelength absorber for series-connected multi-junction PSCs to obtain high VOC approaching 2 V. |
