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有機薄膜太陽電池 (organic photovoltaics, OPV) は，低温で安価な塗布プロセスによって製造可能な次世代太陽電池として注目されている．OPVの発電層には一般的に二種類の有機半導体材料の混合膜を用いるが，これに吸収帯の異なる有機半導体材料を第三成分として加えることで，光吸収領域が拡大しエネルギー変換効率を向上させることができる．本稿では，p型材料として高結晶性ポリマー，n型材料としてフラーレン誘導体を用い，第三成分として非フラーレンn型材料を加えた三元系OPVについて紹介する．この三元系素子では，第三成分はホストとなるポリマーおよびフラーレン誘導体より含有量が非常に少ないものの，ポリマーと同様の外部量子収率を示すことで，ホスト二元系素子に比べて大幅に効率が向上した．これは，光干渉効果により第三成分の光吸収が増幅されることに起因する．第三成分を少量加えるだけで高効率化が可能であるため，今後のOPV開発において重要な手法として期待される．, Significant improvement in the power conversion efficiency of organic photovoltaics has been made in the last decade. Ternary blend OPVs (organic photovoltaics), in which three organic semiconductors are blended to absorb wide range of the incident light, have shown to be an important strategy for improving the efficiency. Here, we show a ternary blend OPV system that used a high-crystalline polymer and a fullerene derivative as the host binary blend system and a nonfullerene n-type material as the third component. It was found that even with a small amount of the third component, optical absorption can be enhanced by the optical interference effect, which significantly boosted the efficiency of the ternary blend cell compared to the binary blend cell.

Organic pn junction solar cells were fabricated by direct substrate laminating method. Poly(3-hexylthiophene) (P3HT) and [6, 6]-phenyl C61-butyric acid methyl ester (PCBM) were dissolved in chloroform (1wt%) and spin-coated on indium tin oxide (ITO) glass substrates, respectively. In the laminating, an ionic liquid, 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI), was used as adhesive layer. The photovoltaic properties of the devices strongly depended on the voltage sweep direction, because the anions and cations were oriented in the films by applied voltage. In the negative sweep direction, the devices showed short-circuit current density (Jsc) of 0.11 mA/cm2, open-circuit voltage (Voc) of 1.2 V, and power conversion efficiency (PCE) of 0.15%. We have demonstrated that pn junction can be formed only by physical contact with ionic liquid as adhesive layer.

Polymer solar cells have attracted increasing attention recently because they are lightweight, flexible, and colorful, and in addition, are suitable for high-throughput production by printing techniques. In this review, we will describe recent progress in polymer solar cells in terms of photovoltaic conversion mechanism and efficiency. As for the photovoltaic conversion mechanism, recent studies have shown that an energy offset in the HOMO or LUMO level would be not necessary for excitons to be dissociated into free charge carriers in polymer solar cells. This is one of the hottest topics in this community. As for the photovoltaic performance, ternary blends and non-fullerene acceptors have a great impact on the improvement in power conversion efficiency. As a result, the efficiency has exceeded 17％ for tandem polymer solar cells based on non-fullerene ternary and binary blends. We also mention the future direction of polymer solar cells.

Photovoltaic properties of polymer-fullerene bulk heterojunction solar cells were improved by ionic liquid doping. We used trihexyl [tetradecyl] phosphoniumbis [trifluoromethylsulfonyl] amide (P66614TFSI) as an ionic liquid. The blends of poly(3-hexylthiophene) (P3HT) and [6，6]-phenyl C61-butyric acid methyl ester (PCBM)were dissolved in chloroform and spin-coated on indium tin oxide (ITO) glass substrates followed by drop-casting of P66614TFSI. The films were annealed at 120 ℃ to osmose the P66614TFSI under a nitrogen purge. The photovoltaic properties of P66614TFSI-doped devices showed short-circuit current density(Jsc) of 18.9 mA/ｃｍ2，open-ciｒcuit voltage (Voc) of 0.53 V ，fill facer(FF) of 0.29，and power conversion efficiency (PCE) of 2.94%. After ionic liquid doping，the devices exhibited a 5-fold increase in PCE.

Organic p-n heterojunction photovoltaic cells consisting of phthalocyanine (ZnPc) Fullerene (C60) and molybdenumtrioxide (MoO3) as buffer layer were fabricated by vacuum deposition method and their rectification and photovoltaic properties were investigated. The J-V characteristics of the device under 1 sun simulated solar illumination exhibited a power conversion efficiency(PCE) of 1.098 % with a Voc of 0.380 V, a Jsc of 7.476 mA cm−2, and a FF of 0.387. It was found that the durability of the device under vacuum, Ar gas or O2 gas enhances by incorporating MoO3 buffer layer.

The production of carbon-related nano-particles including fullerenes and nanotubes under microgravity condition showed clear differences in their yields and diameters from those produced under normal gravity condition. According to numerical analysis, it was expected that the cooling rate of a carbon rich vapor in a buffer gas would be more moderate under the microgravity than in the normal gravity. The gas evaporation under microgravity was expected to be advantageous in synthesizing any clusters having complex structures that required long residence times of their precursor clusters in high temperature state, such as endohedral metalloflluerenes and single-walled nanotubes., 資料番号: AA0063349013

資料番号: AA0063347006

Fullerene C_ is a soccer ball-like molecule which has 12 pentagons and 20 hexagons. All carbon atoms in this molecule take the same chemical bond style, a single 108° angle and two 120° angles, for chemical bonds. Fullerene pointer developed in this laboratory makes it possible to set the chemical bond points having the above bond angles on the surface of a carbon ball. Firstly, 12 pentagons were made using 108° angle points on a carbon ball, and then these pentagons were connected to each other using 120° angle points. During the connection of pentagons, hexagons were formed naturally and the shape of the molecular model became that of a soccer ball. Thus, anyone is able to make a molecular model of fullerene easily.

資料番号: AA0045919018

Gas temperature distribution around the gravity-free gas arc is investigated by means of the parabolic flight experiment and the special gas temperature distribution with spherical symmetry is obtained. The production rate of single-walled carbon nanotubes increases and the thickness of the tubes tends to increase under the gravity-free condition., 資料番号: AA0045438052

Synthesis of ionic hydrocarbons by the combination of the tert-butyl-C60 anion (t-BuC60-) and a tropylium or cyclopropenylium ion is described. The reactions of t-BuC60- and carbocations (R+) with pKR+ values ranging from 3.88 to 10.0 resulted in regioselective carbon-carbon bond formation to form 1, 4-adducts, t-BuC60-R. These covalent hydrocarbons underwent reversible heterolysis into t-BuC60- and R+ in polar solvents. Thermodynamic studies indicated that the heterolysis is promoted by the specific solvation of the produced ions. In contrast, t-BuC60- and tris (guaiazulenyl) cyclopropenylium ion gave a hydrocarbon salt. The ionic nature of this material was demonstrated by the vis/NIR and IR absorption spectra in the solid state. Electrical conductivity measurements indicated that this salt behaves as a strong electrolyte in DMSO. Single-electron reduction of C60 with the crystal violet radical also gave a carbocation-carbanion salt, composed of the crystal violet cation and C60·-.

The effects of the pulse parameters (frequency, duty ratio) of the pulse current and the hybrid ratio, i. e. ratio of the pulse current to the hybrid current, on the fullerene yield were studied experimentally. The hybrid carbon arc device, which was superimposed the square-wave pulse current upon the DC arc was used in this study. As a result, it was found that the fullerene yield for the hybrid arc was about twice as large as the one for DC arc and the fullerene yield was influenced by pulse parameters and strongly by the distribution of C2 density in the arc.

Bulk samples of C_ were consolidated by means of the high-pressure technique at pressures of up to 5.4 GPa and temperatures of up to 800℃. The as-pressed samples showed pressure-induced phase transition related to the polymerization. After annealing in a vacuum atmosphere, they converted to the normal phase C_. The mechanical properties such as elastic moduli, compressive strength, hardness, friction coefficient and wear rate were measured. The results indicated the improvement of the mechanical properties in the polymerized phase sample in comparison with the normal phase sample. It was due to the new covalent bond among neighboring molecules in the polymerized phase.

資料番号: AA0048091018

資料番号: AA0047901027

Doctor of Philosophy in Engineering, Doshisha University