Isothermal Crystallization of PC61BM in Thin Layers Far below the Glass Transition Temperature
Isothermal Crystallization of PC61BM in Thin Layers Far below the Glass Transition Temperature,Crystal Growth & Design,15(11): 5614-5623,2015 (NOV).
An isothermal study was performed on 1.25 μm thin layers of PC61BM, a benchmark acceptor for organic photovoltaics. Using fast scanning chip calorimetry allowed for a scanning rate of 30 000 K·s−1, ensuring that all non- isothermal effects were avoided. The effect of isothermal treatments above and far below the glass transition was investigated. It was proven that PC61BM can crystallize below its glass transition, a behavior seen before for several organic glasses. Isothermal treatments as far as ca. 100 K below the glass transition lead to an initial enthalpic relaxation process around the glass transition, which over time gives rise to crystals melting around 300 °C. These observations show a remarkable similarity with the two-step nucleation mechanism documented in the literature. A standard crystallization process was observed for treatments above the glass transition. By combining chip calorimetry pretreatments with atomic force microscopy, different crystal morphologies were visualized for these two types of thermal treatments, a behavior reminiscent of other organic glasses that crystallize below the glass transition.
author = "Van den Brande, N.; Van Assche, G.; Van Mele, B.",
title = "Isothermal Crystallization of PC61BM in Thin Layers Far below the Glass Transition Temperature",
journal = "Crystal Growth & Design",
year = "2015",
volume = "15",
number = "11",
pages = "5614-5623",
month = "NOV",
doi = "10.1021/acs.cgd.5b01331",
note = "",