We present measurements of absorbance and photoluminescence (PL) for films of poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) as a function of temperature (T) and time (t) of illumination. While having no detectable influence on absorbance of this conjugated polymer, our experiments clearly revealed that illumination of PDOPT caused a significant increase in the PL intensity (I PL (T,t)), that is, the emission probability of PDOPT. Without illumination, we always observed a decrease in I PL with time. An increase in I PL was only detectable when the sample was illuminated. Interestingly, while absorption and emission of photons occur on a time scale of nanoseconds, the herereported changes in the emission probability were slow and occurred on a time scale of minutes to hours. The influence of illumination on changes in I PL (T,t) was qualitatively similar for slowly and rapidly crystallized PDOPT, that is, the degree of crystallinity was not decisive for the observation. The rate of the increase in I PL depended clearly on the power of the illumination light source. As a function of the illumination time, the change in I PL (T,t) was nonmonotonic and depended on sample temperature. We speculate that changes in polymer interactions caused by excited electronic states might have induced slow changes in polymer conformations.

We investigated non-isothermal and isothermal crystallization of spin-coated poly(3-hexylthiophene) thin films prepared from the melt by in-situ ultraviolet-visible absorption spectroscopy. Analyzing the absorption spectra according to the Franck-Condon principle allowed for a quantitative assessment of the degree of crystallinity as well as the quality of order within crystalline regions of the films. Measured at room temperature, we observed a similar crystallinity for all differently crystallized films. The highest quality of order, however, was found for the P3HT film cooled slowly from the melt. These results were in full agreement with the results obtained by X-ray diffraction and calorimetry measurements. Consistently, in spite of similar crystallinities, atomic force microscopy images did not show a well-defined structure of ordered domains of preferentially aligned lamellae for the films rapidly cooled from the melt. In addition, heating the P3HT films in a specific range of temperature showed no change in crystallinity in spite of a continuous loss of order quality. Our results revealed that crystallinity and crystalline quality could behave differently while processing a semicrystalline polymer.

Films of Fe-doped In 2 O 3 that were deliberately fabricated so they contained Fe 3 O 4 nanoparticles were deposited on sapphire substrates by pulsed laser deposition at low oxygen pressure. The concentration of Fe was varied between 1% and 5%, and the effect of including 5% of Sn and vacuum annealing were also investigated. Structural analysis indicated a high concentration of Fe 3 O 4 nanoparticles that caused substantial values of the coercive field at room temperature. Transport measurements indicated that the films were metallic, and an anomalous Hall effect was observed for the sample with 5% of Fe. The concentration of nanoparticles was reduced dramatically by the inclusion of 5% of Sn. Magnetic circular dichroism spectra taken in field and at remanence were analyzed to show that the samples had a magnetically polarized defect band located below the conduction band as well as magnetic Fe 3 O 4 nanoparticles. The signal from the defect states near the band edge was enhanced by increasing the number of carriers by either including Sn or by annealing in vacuum.