||STUDY ON NANOSTRUCTURED METAL NANOPARTICLES/ NANOCLUSTERS ENHANCED ORGANIC THIN-FILM SOLAR CELLS
学位の種類: 博士（工学）. 報告番号: 甲第4334号. 学位記番号: 新大院博（工）甲第464号. 学位授与年月日: 平成29年3月23日
Thin-film organic solar cells (OSCs) were fabricated by assembly of thin-film organiclayers with different activities for photovoltaic process. The challenge of OSCs is economical cost, thin-film structure, and fixable substrate. However, the disadvantage of OSCs such as high reflection and low absorption of solar light due to the design of OSCs gives the percent of solar cell efficiency (%PCE) less than it should be. Therefore, increasing %PCE is important topic. By the fabrication of nanoscale structure with variety of metal nanoparticles (i.e. silver and gold nanoparticles (AgNPs and AuNPs)), plasmonic and fluorescence properties were produced and controlled. The plasmonic and fluorescence properties of metalnanoparticles have been used as a light-trapping and light-converting material, respectively, while the thickness of each layer in OSCs is still constant.In our work, the plasmonic enhancement of urchin-like gold nanoparticles (UL-AuNPs) and combination of different plasmonic excitations of silver nanoprisms (mixed-AgNPrs) shows the promising evident for light absorption and light scattering in broadband wavelength in visible range that improve solar cell efficiency. However, plasmonic properties of AuNPs and AgNPs are limited in visible light (400-800 nm). To open another opportunity,gold quantum dots (AuQDs) are used for harvesting UV light and converting to visible light for OSC. By plasmonic and fluorescence enhancement, %PCE of developing OSCs were increased by 5 – 10% when compared with the reference cell. All of metal nanoparticles (i.e.UL-AuNPs, Mixed-AgNPrs and AuQDs) were included in a hole transport layer of OSCs. Furthermore, the aggregation of metal nanoparticles on the hole transport layer and effect to photovoltaic parameters were investigated by UV-vis spectroscopy, atomic force microscope, J-V characteristic, and impedance spectroscopy. The concentration of metal nanoparticles plays an important role to control a aggregation degree on hole transport layer film. This phenomenon induces the plasmonic or fluorescence quenching and generates shortcircuit current that reduce %PCE of OSCs. Moreover, the mechanism of plasmonic orfluorescence enhancement from metal nanoparticles were observed by incident photon-to-current and supported by finite-difference time-domain simulation.