The domain size of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) within the bulk heterojunction of organic photovoltaics (OPVs) is of great importance to the performance and lifetime of the device. This study focuses on the use of polymer-tethered fullerenes (PTFs) as an additive to reduce the initial domain size of PCBM as well as to mitigate the growth of these domains over time that typically results in decreased device efficiency. Films were prepared from a 1:1 mixture of PCBM:P3HT on silicon wafers to approximate a bulk heterojunction system. PTFs were added in concentrations ranging from 0 to 20 percent. The samples were then annealed at 150�C for varying times ranging from 5 to 60 mins and examined by SEM to determine the average PCBM domain sizes for each sample. As expected, the control sample containing no additive showed significant growth in the PCBM domains as the sample was annealed with a final average domain size of 290 �m2. However, addition of as little as 5% PTFs produced average PCBM domain sizes after 60 minutes of annealing of 28 �m2. Addition of 20% PTF resulted in an average PCBM domain size of 2 �m2. Based on these encouraging results, devices containing these architectures were prepared yielding an increase in the lifetime, and in some cases, the efficiency of the device.

Using polymer-tethered fullerenes in bulk hetereojunctions

247th National Meeting (2014)

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