| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 97 === Nano-scaled thermal analysis of optoelectronic polymer thin films was investigated in this research work. A scanning probe microscopy (SPM) integrated with a scanning thermal probe was employed to perform the in-situ thermal analysis and the scanning thermal microscope (SThM) on the surface of thin film materials.
Poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), commonly used in bulk heterojunction photovoltaics, were spin-coated on silicon wafers or ITO-coated glass substrates with film thickness ranged from 30 to 900 nm. Thermal expansion profiles indicated the thermal expansion coefficients and the melting temperatures of P3HT/PCBM samples were both affected by film thicknesses. A series of SThM with various scanning temperatures was conducted for the 2D mapping of surface thermal conductivities. Fluctuations of these thermal conductivities revealed the thermal transitions and/or the phase separations near the material surfaces. Thermal conductivity differentials were maximized at the mapping temperatures of about 80oC and 120oC for pure P3HT and P3HT/PCBM samples, respectively. The first one represented the 80oC glass transition temperature of P3HT, which was usually undetectable in the conventional differential scanning calorimetry. And, the 120oC temperature recognized the optimized thermal annealing of P3HT/PCBM blends, where the phase separation and morphological rearrangement of P3HT and PCBM domains altered the distribution of surface thermal conductivities.
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