| Summary: | 博士 === 國立臺灣大學 === 高分子科學與工程學研究所 === 97 === In this study, we investigate the effect of interface modification of metal oxide on photovoltaic properties of conducting polymer/metal oxide solar cells, systematically.
First, two series of organic molecules with different chemical structures, 2-oligothiophene phosphonic acid with various thiophene rings (T-series) and ω-(2-thienyl) alkyl phosphonic acid with various alkyl chain lengths (N-series), as interface modifier, to investigate the structural effect of modifiers on the performance of organic/inorganic bilayered photovoltaic devices. The results indicate the interface modifier does not affect absorption behavior of P3HT, but PL quenching efficiency as increased with energy bandgap or LUMO of interface modifier decreasing. It reveals the charge separation of organic/inorganic interface will be affected by chemical structures of interface modifier. Therefore, these interface modifiers that with different chemical structures will affect the photovoltaic properties of devices, especially in Voc and Jsc. Voc will decrease with energy bandgap or LUMO of interface modifier decreasing, but does not be affected by alkyl chain length of interface modifiers changed. In addition, Jsc will increase with energy bandgap, alkyl chain length or LUMO of interface modifier decreasing.
Second, we apply the above interface modifiers as surfactant in solution process of blend device system. TEM image indicate the modified ZnO nanorods without large scale aggregation and form a continued path way in P3HT matrix. Therefore, the increased compatibility and contact area between P3HT and ZnO nanorods has been demonstrated. PCE value of modified ZnO nanorods/P3HT polymer blend devices are higher than without modified ZnO nanorods prepared devices. Furthermore, the trends of Voc and Jsc of modified ZnO nanorods/P3HT polymer blend solar cell are consisted with above layered system.
Third, we demonstrate a low leakage current in a blend ZnO nanorods/P3HT polymer solar cell aided by an inherent UV-cutter layer (copper phthalocyanine CuPc). The power conversion efficiency is found to be appreciated from 0.15% to 0.44% and the open circuit voltage from 0.23 to 0.60 V, at post-introduction of UV-cutter, predominantly due to the growth in the shunt resistance of the device. Impedance spectroscopy studies revealed a strong negative photovoltaic effect of ZnO with UV-induced hole-trapping leading to the degradation of the solar cells performance. The incorporation of UV-cutter in the device, achieved by direct growth of CuPc layer between nr-ZnO and anode, has clearly promoted the efficiency and device operation satiability.
Finally, we synthesize a C60 derivative, (1,2-methanofullerene C60)-61,61-dicarboxylic acid, with a 300-400nm absorption region as surface UV filtered surfactant to apply in blend ZnO nanorods/P3HT polymer solar cell. The decreased leakage current behavior of blend ZnO nanorods/P3HT polymer solar cell has been demonstrated. PCE value and operation satiability of (1,2-methanofullerene C60)-61,61-dicarboxylic acid modified ZnO nanorods/P3HT devices are better than N3 dye (P type) modified devices. In addition, 17.5% IPCE value of (1,2-methanofullerene C60)-61,61-dicarboxylic acid modified ZnO nanorods/P3HT device has been revealed.
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