Abstract
A simple technique is demonstrated based on UV-vis spectroscopy that permits the onset of fullerene crystallization to be monitored in polymer:fullerene bulk-heterojunction blends. The growth of fullerene crystals only occurs during thermal annealing above the glass transition temperature (Tg) of the blend. Light scattering due to the presence of micrometer-sized fullerene crystals reduces the apparent transmittance, which can serve as a clear indicator for the upper limit of the Tg. This principle is used to deduce this critical parameter for two high-performance photovoltaic blends that are based on a thiophene-quinoxaline and a thiophene-isoindigo copolymer, respectively. High Tgs of 115 and 145 °C promise good thermal stability. UV-vis spectroscopy is used to monitor the onset of fullerene crystallization in polymer:fullerene bulk-heterojunction blends. Micrometer-sized fullerene crystals grow during thermal annealing and scatter light, which can serve as a clear indicator for the upper limit of the glass-transition temperature of the blend.
| Original language | English |
|---|---|
| Pages (from-to) | 530-535 |
| Number of pages | 6 |
| Journal | Macromolecular Chemistry and Physics |
| Volume | 215 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - Mar 2014 |
Keywords
- bulk heterojunctions
- crystal growth
- glass transition temperature
- organic photovoltaics
- UV-vis spectroscopy
