Molecular engineering for controlling and stabilizing blend morphology of organic solar cells

Abstract

Firstly, a series of polymer donors with different D units in D-A alternating polymers were synthesized to achieve highly efficient organic solar cells. Through introducing different D units, the characteristics of polymers were changed including optical, electrochemical and thermal properties, and it leads differences in photovoltaic and morphological properties in blends with ITIC electron acceptor. We systematically analyzed the properties using appropriate tools such as DFT calculation, GIWAXS and RSoXS. Finally, the highly efficient PCE over than 8% was achieved. Furthermore, we tried to reveal the relationship between relative crystalline behavior of donor to acceptor and other properties of photovoltaic and morphological behavior Second, a new material, 5TRh-PCBM was synthesized to control morphology of OSCs blend films. In strategy of compatibilization donor and acceptor phases by introducing 5TRh-PCBM, the thermal stability of OSCs devices was effectively improved under the heat. We firstly analyzed the effect of compatibilizer in P3HT:$PC_(61)$BM system, which is the most traditional and easiest to observe morphological changes by various tools to measure morphological properties such as optical microscopy, GIWAXS and RSoXS. In addition, to demonstrate that the effect of compatibilizer 5TRh-PCBM is widely applicable to highly efficient system with semi-crystalline or amorphous donor, PTB7-Th:$PC_(71)$BM system was introduced to see the trend of thermal stability as adding 5TRh-PCBM. In conclusion, these researches present one of the guideline of molecular engineering to achieve highly efficient and stable OSCs through controlling and stabilizing blend morphology.