| Summary: | 碩士 === 國立成功大學 === 光電科學與工程學系 === 100 === In this study, we prepared the poly(3-hexylthiophene) (P3HT):Indene -C60 Bisadduct (IC60BA) blend films-based polymer bulk heterojunction (BHJ) solar cells by the co-solvent methods. The host solvent was 1,2-dichlorobenzene (DCB), and mixed with dichloromethane (DCM) or chloroform (CF) as co-solvents. For P3HT, DCM and CF are poor and good solvents, respectively. To investigate the effects of co-solvents on microstructure of the active layers, the P3HT:IC60BA films were characterized by absorption spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, atomic force microscopy (AFM) and X-ray diffraction (XRD). The correlation between the microstructural properties of the active layers and photovoltaic properties of the polymer BHJ solar cells was discussed.
For the photovoltaic properties of the solar cells made by the DCM:DCB co-solvents with the volume fraction of DCM (fm) was below 50%, we observed that the fill factor (F.F.) decreased when the fm was increased, while increasing short-circuit current density (Jsc) and power conversion efficiency. When the fm is below 50%, the increased in JSC can be attributed to higher absorbance arising from thickness contributions. When the fm is higher than 50 %, however, we observed a reduction in the JSC, reflecting the decreased probability of charge carriers transport to the right electrodes due to largely increasing active layer thickness. Above-motioned observations still hold true for the solar cells made by the CF:DCB co-solvents. Microstructural analysis results revealed that the crystalline P3HT in the P3HT:IC60BA blend films were not affected by changing the composition of the DCM:DCB co-solvents. In contrast, we observed more amorphous P3HT contents and smaller grain size of the films made by the CF:DCB co-solvents, thereby poor carrier transport and increased probability of carrier recombination. This provides a reasonable basis for the lower F.F. and Jsc of the solar cells. Finally, we have demonstrated a P3HT:IC60BA blends-based solar cell with high power conversion efficiency of 5.23 % by using the DCM:DCB co-solvent with fm of 50 %
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