| 초록 |
In this study, two wide band gap derivatives of PM7, which are structurally simplified by ester alkyl side chains on trithiophenes instead of fused accepting unit, were utilized as donor in NDI-based all-PSCs. Two different derivatives are investigated depending on the different position of ester alkyl side chains, i.e., two ester groups on first and third thiophenes, respectively, (PM7 D1) and two ester groups on central thiophene (PM7 D2). This simple chemical modification enables light absorption to be effectively blue-shifted maintaining low HOMO energy level. As a result, the highest performance of 9.1% is achieved in PM7 D1 blend film mainly ascribed to the better complementary light harvesting. Additionally, when we examine mechanical properties, elongation property of PM7 D1 and PM7 D2 pristine and blend films is improved compared to that of PM7. This result is mainly attributed to flexible ester groups which are able to release applied stress before the film breaks. |
