<p>In this thesis, the microstructure of organic photovoltaic APFO-3:PC<sub>61</sub>BM bulk-heterojunction blends was examined. Earlier studies have focused on the microstructure after spin coating. This thesis aims to give a better insight into microstructural degradation as the films are annealed above the glass transition temperature, T<sub>g</sub>, and the mixture approaches thermodynamic equilibrium. Electro- and photoluminescence studies indicate that the polymer and PC<sub>61</sub>BM are intermixed on a scale shorter than the exciton diffusion length of 10 nm, even when annealed above T<sub>g</sub>. The temperature stability of APFO-3:PC<sub>61</sub>BM was also investigated with respect to the molecular weight of the polymer. The photovoltaic performance of these blends was found to be stable up to temperatures approaching the glass transition temperature, especially if a high molecular-weight APFO-3 grade was used.</p><p> </p><p>The crystallization of PC<sub>61</sub>BM was also investigated. Above T<sub>g</sub>, PC<sub>61</sub>BM crystallization was found to commence, albeit slowly at temperatures close to T<sub>g</sub>. At elevated temperatures instead, micrometer sized crystals were observed to form. It was also noted that illumination while annealing APFO-3:PC<sub>61</sub>BM thin films above T<sub>g</sub> affected PC<sub>61</sub>BM crystallization, the origin of which is so far unclear although chemical degradation could be largely excluded.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:liu-58559 |
| Date | January 2010 |
| Creators | Bergqvist, Jonas |
| Publisher | Linköping University, Biomolecular and Organic Electronics |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, text |
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