JP5334930B2 - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element having a charge transfer type hetero-junction structure which can obtain a solar cell, a light emitting diode or the like, excellent in durability, electronic physical properties, economic efficiency or the like by using a fullerene polymer film for a part of a component. <P>SOLUTION: A photocell has a hetero-junction structure obtained by laminating an electron supplying conductive polymer film 3 and an electron receiving fullerene polymer film 4 between a pair of electrode 1, 5 at least one of which is light-transmissible. In the formation of respective layers, especially the Raman method and the NEXAFS method are used together to identify the fullerene polymer film 4, and after confirming the polymer film, an upper layer is formed. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a photoelectric conversion element having a charge transfer heterojunction structure having fullerene as a part of a constituent material, for example, as a solar cell or a light emitting diode.

  Conventionally, a silicon pn junction semiconductor or the like has been widely used as a constituent material of a solar cell, and its energy conversion efficiency has improved considerably compared to the initial development.

  As materials for solar cells, there are titania and the like in addition to the above silicon. Recently, fullerene, which is one of carbon compounds, has attracted attention. In the following, the characteristics of fullerene will be described while reviewing the history of discovery and development.

Fullerene is a series of carbon compounds consisting only of carbon atoms, like diamond and graphite. Its existence was confirmed at the end of this century, and it was discovered in the mass spectrometry spectrum of a cluster beam by laser ablation of carbon in 1985. However, it is necessary to wait for another five years before the manufacturing method is actually established, and since 1990 the first fullerene (C ₆₀ ) manufacturing method by arc discharge of a carbon electrode has been found. Since then, fullerenes have been found. Has attracted attention as a carbon-based semiconductor material. (Kratschmer, W .; Fostiropoulos, K .; Huffman, DR Chem. Phys. Lett. 1990, 170, 167. Kratschmer. W .; Lamb. LD; Fostiropoulos, K .; Huffman, DR Nature 1990, 347, 354. )

Fullerene is a spherical carbon C _n (n = 60, 70, 76, 78, 80, 82, 84...) In which an even number of 60 or more carbon atoms are bonded in a spherical shape to form a molecular assembly. is there. Of particular representative of a C ₇₀ to C ₆₀ with 70 carbon atoms mentioned in the beginning it is 60. Among them, C ₆₀ fullerene has a polyhedral structure called a truncated icosahedron that has a regular pentagon formed by cutting off all the vertices of the regular icosahedron, and all of the 60 vertices are as shown in FIG. It has a so-called soccer ball type molecular structure occupied by carbon atoms. On the other hand, _C70 has a rugby ball type molecular structure as shown in FIG.

The C ₆₀ crystal has a C ₆₀ molecule arranged in a face-centered cubic structure, has a band gap of about 1.6 eV, and can be regarded as a semiconductor. In its pure state, it has an electrical resistance of about 10 ¹⁴ Ω / cm. Then, there is a vapor pressure of about 1 mmTorr at 500 ° C., and a thin film can be deposited by sublimation. In addition to C ₆₀ , fullerene molecules can be easily vaporized under vacuum or reduced pressure, and thus are easy to form a deposited film.

However, since the fullerene molecules such as C ₆₀ and C ₇₀ rich in most mass production dipole moment is zero, the deposited film obtained therefrom is not work only van der Waals forces between the molecules, the strength to Vulnerable. Therefore, when this deposited film is exposed to the air, oxygen, water molecules, etc. are likely to diffuse into the gaps between the fullerene molecules (see FIG. 34), resulting in not only structural deterioration but also electronic properties. May have adverse effects. Such fragility of the fullerene-deposited thin film becomes a problem in terms of device stability when fullerene is applied to the production of a thin film electronic device. Furthermore, since the paramagnetic center is expressed by oxygen molecules diffused and entered between the fullerene molecules, there is a problem in terms of the stability of the thin film characteristics.

  In order to overcome such problems, a so-called fullerene polymer film production method in which fullerene molecules are polymerized has been proposed in recent years. A typical example is a method of forming a fullerene polymer by light induction. ((A) Rao, AM; Zhou, P .; Wang, K.-A; Hager, GT; Holden, JM; Wang, Y .; Lee, W.-T .; Bi, X.-X .; Eklund , PC; Cornett, DS; Duncan, MA; Amster, IJ Science 1993, 256, 955. (b) Cornett, DC; Amster, IJ; Duncan, MA; Rao, AM; Eklund. PCJ Phys. Chem. 1993, 97, 5036 (c) Li, J .; Ozawa, M .; Kino, N .; Yoshizawa, T .; Mitsuki, T .; Horiuchi, H .; Tachikawa, O .; Kishio, K .; Kitazawa, K. Chem. (Phys. Lett. 1994, 227, 572.)

  In this method, a fullerene vapor-deposited film formed in advance is irradiated with light after vapor deposition. However, due to volume shrinkage that occurs during polymerization, innumerable cracks are easily generated on the film surface, which is problematic in terms of strength. In addition, with this method, it is extremely difficult to form a uniform thin film having a large area.

  In addition, it is known that fullerene polymer films can be formed by applying pressure or heat to fullerene molecules, or by causing fullerene molecules to collide with each other. It is difficult to get. (Molecular collision method (a) Yeretzian, C .; Hansen, K .; Diederich, F .; Whetten, RL Nature 1992, 359, 44. (b) Whetten, RL; Yeretzian, C. Int. J. Mod. Physics 1992, B6, 3801. (c) Hansen, K .; Yeretzian, C .; Whetten, RL Chem. Phys. Lett. 1994, 218, 462. (d) Seifert, G .; Schmidt, R. Int. J. Mod Phys. 1992, B6, 3845. Ion beam method (a) Seraphin, S .; Zhou, D .; Jiao, JJ Mater. Res. 1993, 8, 1995. (b) Gaber, H .; Busmann, H. -G .; Hiss, R .; Hertel, IV; Romberg, H .; Fink, J .; Bruder, F .; Brenn, RJPhys.Chem, 1993,97,8244. Pressure method (a) Duclos, SJ; Brister, K .; Haddon, RC; Kortan, AR; Thiel, FA Nature 1991, 351, 380. (b) Snoke, DW; Raptis, YS; Syassen, K. 1 Phys. Rev. 1992, B45, 14419. (c) Yamawaki, H .; Yoshida, M .; Kakudate, Y .; Usuda, S .; Yokoi, H .; Fujiwara, S .; Aoki, K .; Ruoff, R .; Malhotra, R .; Lorents, DJPhys. Chem. 1993, 97, 11161. (d) Rao, CNR; Govindaraj, A .; Aiyer, HN; Seshadri, RJ Phys. Chem. 1995, 99, 16814.)

  On the other hand, the plasma polymerization method and the microwave (plasma) polymerization method previously proposed by the present inventors are worthy of attention as a fullerene polymerization method (or film forming method) that replaces these conventional methods. (For example, Takahashi, N .; Dock, H .; Matsuzawa, N .; Ata, M.J. Appl. Phys. 1993, 74, 5790.). The film of fullerene polymer (FIGS. 32 and 33) obtained by such a method is a thin film formed by polymerizing fullerene molecules through an electronically excited state, and the strength is significantly increased compared to a fullerene-deposited thin film. It is dense and flexible. And since the electronic properties hardly change in vacuum or in the air, it is considered that the dense thin film structure effectively suppresses the diffusion of oxygen molecules into the film. In fact, the generation of fullerene multimers constituting a thin film by such a method can be known by time-of-flight mass spectrometry by laser ablation.

Regardless of the type of plasma method, the electronic physical properties of the fullerene polymer film are considered to depend largely on the polymerization form. The mass spectrometry result of the C ₆₀ polymer film actually obtained by the microwave plasma method is very similar to that of the C ₆₀ argon plasma polymer thin film previously reported by the inventors [Ata, M .; Takahashi, N .; Nojima, KJPhys. Chem. 1994, 98, 9960. Ata, M .; Kurihara, K .; Takahashi, J. Phys. Chem. B 1996, 101, 5.].

The fine structure of the fullerene polymer can be estimated by time-of-flight mass spectrometry (TOF-MS) with pulsed laser excitation. In general, a matrix assist method is known as a method for nondestructively measuring a high molecular weight polymer. However, since there is no solvent that dissolves the fullerene polymer, it is difficult to directly evaluate the actual molecular weight distribution of the polymer. Mass evaluation by LITOF-MS (Laser Desorption Ionization Time-of-Flight Mass Spectroscopy) is also due to the absence of an appropriate solvent and the inability to apply the matrix assist method because C ₆₀ reacts with matrix molecules. Therefore, it is difficult to accurately evaluate the mass distribution of the actual fullerene polymer.

Structure of C ₆₀ polymer may be C ₆₀ from profile multimers peak position and dimer of LDITOF-MS observed by ablation laser power enough not undergo polymerization estimates. For example, LDIOF-MS of a C ₆₀ polymerized film obtained with a plasma power of 50 W shows that the process involving the loss of four carbons is most probable in the polymerization between C ₆₀ molecules. That C ₁₂₀ in the mass regions of the dimer are minor products, are C ₁₁₆ to produce the highest probability.

Further, according to the calculation of C ₆₀ dimer at a semi-empirical level, this C ₁₁₆ is considered to be a D _2h symmetric C ₁₁₆ as shown in FIG. This is obtained by recombination of C ₅₈ , and it is reported that C ₅₈ is generated by desorption of C ₂ from a high electronic excited state including an ionized state of C ₆₀ [(a) Fieber-Erdmann , M. et al, Z. Phys. D1993, 26, 308. (b) Petrie, S. et al, Nature 1993, 356, 426. (c) Eckhoff, WC; Scuseria, GE; Chem. Phys. Lett. 1993, 216, 399. ].

If previously coupled with 2 molecules this open-shell C ₅₈ molecules two 5-membered ring is translocation into adjacent structures, C ₁₁₆ shown in FIG. 5 is obtained. However, the present inventor believes that the [2 + 2] cycloaddition reaction (reaction product is shown in FIG. 4) is caused by an excited triplet mechanism in the initial stage of plasma polymerization of C ₆₀ . In addition, as described above, C ₁₁₆ is generated with the highest probability because (C ₆₀ ) ₂ cyclobutane generated from the electronically excited triplet state of C _{60 by} a [2 + 2] cycloaddition reaction as shown in FIG. This is thought to be due to the elimination of the four SP ³ carbons formed and the recombination of the two C ₅₈ open shell molecules.

For example, when irradiated with strong pulse laser light in the C ₆₀ crystallites on ionization Tagento of TOF-MS, but the fullerene molecules as with the microwave plasma polymerization method polymerization occurs via an electronic excited state, the C ₆₀ photopolymer Along with the peak, ions such as C ₅₈ and C ₅₆ are also observed.

However, since fragment ions such as C ₅₈ ²⁺ or C ₂ ⁺ are not observed, fragmentation from C ₆₀ ³⁺ directly to C ₅₈ ²⁺ and C ₂ ⁺ as described in the aforementioned Fieber-Erdmann et al. It is unthinkable to do in this case. Also, when the film to vaporize C ₆₀ with C ₂ F ₄ gas plasma, only adducts of fragment ions of F or C ₂ F ₄ of C ₆₀ is observed in its LDITOF-MS, C ₆₀ double No coalescence is observed. Thus, LDIOF-MS in which no C ₆₀ polymer is observed has a feature that ions such as C ₅₈ and C ₅₆ are not observed. These observations are also supported a loss of C ₂ occurs from the through C ₆₀ polymer.

The next question is whether the C ₂ loss occurs directly from 1,2- (C ₆₀ ) ₂ by the [2 + 2] cycloaddition reaction shown in FIG. 4 in the plasma polymerization. Mouri and Osawa et al. Have proposed the structure relaxation process of 1,2- (C ₆₀ ) ₂ as follows: [(a) Murry, Rlet al, Nature 1993, 366, 665. Strout, DL et al, Chem. Phys. Lett. 1993, 214, 576. Osawa, E. Personal communication].

In both cases, in the initial stage of structural relaxation of 1,2- (C ₆₀ ) ₂ shown in FIG. 4, C ₁₂₀ (b) in FIG. 6 in which the most strained 1,2-C—C bond at the cross-link site was cleaved. Via the Stone-Wales rearrangement (Stone, AJ; Wales, DJ Chem. Phys. Lett. 1986, 128, 501. (b) Satio, R. Chem. Phys. Lett. 1992, 195, 537.) It is assumed that C ₁₂₀ (d) in FIG. 8 is generated from C ₁₂₀ (c) in FIG. To C ₁₂₀ energetically destabilized when rearranges to (b) in Figures 4-6 of the 1,2- (C ₆₀₎ 2, but further C ₁₂₀ (d in FIG. 8 from C ₁₂₀ (c) of FIG. 7 ) And become stable again as it is rearranged.

After this way the loss of nC ₂ observed in the polymerization of C ₆₀ by plasma induced, its either initial process and considered in FIG. 4 1,2-(C ₆₀₎ from happen directly, or this is to some extent structural relaxation Although no clear knowledge has been obtained as to whether this occurs, the observed C ₁₁₈ has a structure as shown in FIG. 9 due to C ₂ detachment from C ₁₂₀ (d) in FIG. 8 and recombination of dangling. Conceivable. Also, C ₁₁₆ as shown in FIG. 10 is obtained by desorbing two carbons of the ladder cross link of C ₁₁₈ in FIG. 9 and recombining the dangling. When an odd number of clusters TOF-MS of the dimer is from the stable of and structure that is hardly observed, than the loss of C ₂ occurs directly from _{1,2- (C 60) 2, C} 120 in FIG. 8 It seems that it makes more sense to think that it happens via (d).

In addition, Osawa et al. Described in the above literature that a D _5d symmetric C ₁₂₀ structure can be obtained from C ₁₂₀ (a) through structural relaxation by multi-stage Stone-Wales dislocations. The structure of this C ₁₂₀ intended to graphite structure of C ₇₀ molecules extends to C _120, interesting in that it suggests that nanotubes are obtained from C ₆₀ polymer. However, in the formation of the polymer by plasma irradiation, as far as the TOF-MS of the C ₆₀ polymer is seen, the process of structural relaxation with loss of C ₂ takes precedence over the structural relaxation by such multistage rearrangement reaction. Conceivable.

In general, spin transition between ¹ (π−π ^* ) − ³ (π−π ^* ) is forbidden for planar conjugated compounds in which the π orbit and σ orbit intersect at right angles, and it is acceptable when the σ orbit is mixed by vibronic interaction. Become. In the case of C _60, the π orbital and the σ orbital are mixed due to the non-planarity of the π conjugated system, and therefore the inter-term crossover due to spin-orbit interaction between ¹ (π−π ^* ) − ³ (π−π ^* ) becomes possible, high photochemical reactivity of C ₆₀ is provided. The high symmetry of the truncated icosahedron of the C ₆₀ molecule causes a severe forbidden law in the transition between electronically excited states and vibrational levels, but the difference in spin multiplicity (π-π ^* ), which is forbidden for planar molecules. The feature of the behavior of the electronically excited state of fullerene, particularly C ₆₀ , is that the transition between these states is allowed.

The plasma polymerization method can also be applied to the polymerization of _C70 molecules. However, if the polymerization between C ₇₀ molecules, it is not easier than the case of the C ₆₀ to understand the mechanism. Therefore, for convenience, with the aid of the numbering of the carbon atoms of C ₇₀ as shown in FIG. 11, I want to explain as much as possible to understand easily.

105 C—C bonds of C ₇₀ are C (1) -C (2), C (2) -C (4), C (4) -C (5), C (5) -C (6 ), C (5) -C (10), C (9) -C (10), C (10) -C (11), C (11) -C (12) They are classified into C bonds, of which C (2) -C (4) , C (5) -C (6) is a double bond of the same extent as C = C bond of C _60. The π electrons of the 6-membered ring including C (9), C (10), C (11), C (14), and C (15) of this molecule become non-polarized to form a 5-membered ring C (9 ) -C (10) bond is double-bonded, and C (11) -C (12) bond is single-bonded. C polymerizing double bonds of _{C 70 (2) -C (4} ), C (5) -C (6), C (9) -C (10), the C (10) -C (11) Think. The C (11) -C (12) bond is almost a single bond, but since it is a bond across two 6-membered rings (6,6-ring fusion), the addition reactivity of this bond is also examined.

First, consider the [2 + 2] cycloaddition reaction of C _70. From the [2 + 2] cycloaddition reaction of 5 types of C—C bonds, 25 types of C ₇₀ dimers can be obtained, but for the convenience of calculation, only 9 types of addition reactions between the same C—C bonds are obtained. think of. Table 1 shows the heat of reaction (ΔH _f ⁰ (r)) during the formation of C ₇₀ to C ₁₄₀ of two molecules at the MNDO / AM-1 and / PM-3 levels.

表中、ΔＨ_f ⁰(r)ＡＭ−１及びΔＨｆ°（ｒ）ＰＭ−３とは、J. J. P. Stewartによる半経験的分子起動法であるＭＮＤＯ法のパラメタリゼーションを用いる場合の反応熱の計算値である。

In the table, ΔH _f ⁰ (r) AM-1 and ΔHf ° (r) PM-3 are calculated values of the heat of reaction when using the parameterization of the MNDO method, which is a semi-empirical molecular starting method by JJP Stewart. .

In the table, C ₁₄₀ (a) and (b), C ₁₄₀ (c) and (d), C ₁₄₀ (e) and (f), and C ₁₄₀ (g) and (h) are C (2) -C ( 4), an anti-syn isomer pair of C (5) -C (6), C (9) -C (10) and C (10) -C (11) bonds. In the addition reaction between C (11) -C (12) bonds, only D _2h symmetric C ₁₄₀ (i) is obtained. These structures are shown in FIGS. FIG. 12 shows the initial structure of the C ₇₀ polymer by the most stable [2 + 2] cycloaddition reaction.

From Table 1, no energy difference between the anti-syn isomers is observed. The addition reaction between the C (2) -C (4) and C (5) -C (6) bonds is as exothermic as the C ₆₀ addition reaction, and conversely C (11) -C (12) The addition reaction between the bonds is highly endothermic. By the way, although the C (1) -C (2) bond is clearly a single bond, the reaction heat of the cycloaddition reaction between these bonds is +0.19 and -1.88 kcal at the AM-1 and PM-3 levels, respectively. / Mol, which is almost equal to the heat of reaction of C ₁₄₀ (g) and (h) in Table 1. This suggests that the addition reaction between C (10) -C (11) bonds cannot occur thermodynamically. Therefore, the addition polymerization reaction between _C70 molecules occurs preferentially at C (2) -C (4) and C (5) -C (6) bonds, and polymerization between C (9) -C (10) bonds. Even if it happens, the probability is low. Incidentally, a single binding C (11) -C (12) the heat of reaction between the bond C (1) -C (2) become larger exothermic than the reaction heat of linkages, C ₁₄₀ (i) This is considered to be due to the extremely large distortion of the cyclobutane structure, particularly the C (11) -C (12) bond. In order to evaluate the effect of overlapping the 2p ² lobes of sp ² carbon adjacent to the cross-link bond during such [2 + 2] cycloaddition, a C ₇₀ dimer, a C ₇₀ -C ₆₀ polymer, and The heat of formation of C ₇₀ H ₂ was compared. Although detailed numerical data is omitted, it is considered that the effect of this overlap is almost negligible over C ₁₄₀ (a) to (h). However, this is only about the calculation of the MNDO approximation level.

As for the mass distribution in the vicinity of the dimer of the polymerized film of C ₇₀ by LDIOF-MS, the dimer such as C ₁₁₆ and C ₁₁₈ is the main product. Next, similar to the process of obtaining D _2h -symmetric C ₁₁₆ from C ₆₀ , the four carbon atoms forming the cyclobutane of the dimer (C ₇₀ ) ₂ are eliminated and the remaining C ₆₈ is recombined. think about the structure of the C _136. These structures are shown in FIGS. Table 2 shows the relative comparison of the heat of formation of C ₁₃₆ (ΔH _f ^0).

但し、表２中のΔＨ_f ⁰ＡＭ−１、ΔＨ_f ⁰ＰＭ−３、クロスリンク、結合長は、前記表１と同様である。

However, ΔH _f ⁰ AM-1, ΔH _f ⁰ PM-3, cross link, and coupling length in Table 2 are the same as those in Table 1.

C ₁₃₆ (a)-(i) corresponds to C ₁₄₀ (a)-(i), for example, C (2), C (4) forming a cross link with C ₁₄₀ (a) is In C ₁₃₆ (a), it is desorbed. The carbons involved in the four cross links of C ₁₃₆ (a) are C (1), C (3), C (5) and C (8), which are SP ² carbons. Since C ₁₄₀ (c) was predicted to be the most stable structure at the PM-3 level among the dimers shown in Table 1, C ₁₃₆ (c) obtained from C ₁₄₀ (c) is shown in Table 2. ΔH _f ^{0 of} c) was used as a reference for comparison. From Table 2, it can be seen that the structure of C ₁₃₆ (a) and (b) is greatly stabilized, and that C ₁₃₆ (e), (f) and (i) are destabilized. Further, when the calculated values of ΔH _f ⁰ per unit carbon atom of all C ₁₄₀ and C ₁₃₆ structures are evaluated, it is C ₁₄₀ (a) and (b) that structure relaxation occurs in the process from C ₁₄₀ to C ₁₃₆ structure. Only the process from C _{136 to} (a) and (b). Therefore, from the calculation of MNDO approximation level, in the cross-linking of the C _70, not only the site of the [2 + 2] cycloaddition reaction of the initial process is limited to the vicinity of the 5-membered ring at both ends through which molecules spindle, C ₁₃₆ cross-linked structure of the π-conjugated system such as well, C (2) -C (4 ) to be limited only to C ₁₃₆ obtained from a dimer of C ₇₀ by cycloaddition reaction between binding it is indicated. FIG. 13 shows a more stable molecular structure of _C136 generated in the relaxation process of the structure shown in FIG.

The conductivity of the polymer film of C ₆₀ obtained by such an electromagnetic wave-induced polymerization method such as plasma is semiconducting, and the band gap evaluated from the temperature dependence of dark current is about 1.5 to 2 eV. It is also a feature of the polymerized film that the influence of oxygen diffusion in the atmosphere is significantly less than that of the deposited film. The dark current of the C ₆₀ polymer film obtained at a microwave power of 200 W is about 10 ⁻⁷ to 10 ⁻⁸ S / cm, whereas the C ₇₀ polymer film obtained at the same microwave power is 10 ⁻¹³ S / cm. The following is almost an insulator. Such a difference in electrical conductivity of the polymer film is considered to be due to the structure of the polymer film. For C ₆₀ polymerized film, [2 + 2] cycloaddition reaction with 1,2-(C _{60) 2} dimer of cross-linking in Figure 4, one of the C ₆₀ of the two molecules is open shell biradical state Like the cross-link bond, it is considered that it does not contribute to the improvement of conductivity. On the other hand, an intermolecular cross link such as C ₁₁₆ forms a π-conjugated system, which is considered to contribute to improvement of conductivity. Crosslink structures such as C ₁₁₈ , C ₁₁₄ , and C ₁₁₂ are currently under investigation, but contribute to conductivity, consisting of carbon desorption and recombination at the 1,2- (C ₆₀ ) ₂ crosslink sites. This is considered to be a π-conjugated cross link.

Usually, conductivity does not increase linearly with the number of conductive crosslinks between fullerene molecules, but should vary greatly beyond the penetration limit by a certain number. As described above, not only [2 + 2] is a low probability of cycloaddition response compared to C ₆₀ only in the case of C _70, structural relaxation also particular from C ₁₄₀ to the conductive cross-link structure, such as C ₁₃₆ It is thought that it can occur only at the site. Thus although the polymer film of C ₆₀ number of contributing crosslinks conductive exceeds many penetration limit penetration to the limitation of the formation of low polymerization of probability and conductive cross-linked in the case of C ₇₀ The fact that the limit is not exceeded is considered to be the cause of the large difference in conductivity between the two.

  As described above, from the discovery of fullerene molecules, the deposited film and polymer film, and further the mechanism of polymerization have been explained, but here we will return to the solar cell at the beginning.

  The material called fullerene has the potential to provide a solar cell that is economically and physically improved, and in fact, several solar cells comprising fullerene have been proposed (see below). Patent Documents 1 to 5: Japanese Patent Nos. 9656473, 95230248, 99325116, USP 5171373, WO9405045, and the like.

  However, all of the proposed solar cells are common in that they use fullerene vapor deposited films, so the problems arising from the weakness of the vapor deposited films described above, especially the problems related to durability and electronic properties, are still unresolved. Remains.

  By the way, the fullerene polymer film belonging to the same fullerene system as the above-mentioned vapor-deposited film shows sufficient durability due to excellent physical properties such as no oxygen diffusion to the polymer bulk. There has never been an attempt to use construction materials for fabrication.

  The main reason for this is that the fact that industrial fullerene polymerization technology has been developed is still shallow, but there is also a method that can accurately identify fullerene polymer films by non-destructive methods. It is mentioned that it has not been established yet.

  A method such as nuclear magnetic resonance is also known as a means of clarifying the linking of the carbon skeleton of carbon compounds, but for carbon-based thin films such as fullerene polymer films, it is conductive. Depending on this, the pattern of free induction decay is not clearly observed, and measurement is often difficult due to the effect of transverse relaxation on the nuclear spin caused by dangling unpaired spin.

  In addition, this nuclear magnetic resonance method is difficult to magically spin an individual sample, and is not suitable as a means for monitoring structural changes in a carbon-based thin film material.

  The present invention has been made in order to improve the above circumstances, and its purpose is to establish a non-destructive identification method for a fullerene polymer film, and to apply durability to the laminated structure by applying the polymer film to a laminated structure. Another object of the present invention is to provide a charge transfer heterojunction structure and a method for producing the same, which can provide solar cells and the like having improved various physical properties including electronic properties.

  That is, the charge transfer heterojunction structure of the present invention is characterized in that a conductive organic film and a fullerene polymer film are laminated between a light-transmitting electrode and its counter electrode. .

  The method for producing a charge transfer type heterojunction structure of the present invention includes a step of forming a light transmissive electrode, a step of forming a conductive organic film, a step of forming a fullerene polymer film, and a counter electrode. And forming another constituent layer after identifying the fullerene polymer film.

  The identification is most preferably performed by using both the Raman method and the Nexafs method (NEXAFS: Near-Edge X-ray Fine Structure).

  In the heterojunction structure of the present invention, an electron-donating conductive organic film and an electron-accepting fullerene polymer film are laminated between a pair of electrodes having at least one light-transmitting property. Photoinduced charge transfer is possible, and it is suitable for solar cells and light emitting diodes. Since a fullerene polymer film is used as a part of the constituent material, durability and electronic properties are further improved as compared with the case of using a fullerene vapor deposition film. In the case of a vapor-deposited film, the characteristics are easily lost in about one day during the evaluation in the atmosphere. However, when converted into a polymer, the characteristics hardly change even after one month.

  In particular, when applied to solar cells, it is extremely low-cost and lightweight compared to conventional silicon pn junction solar cells, and a thin film with excellent flexibility is possible, and the energy conversion efficiency is inferior. Furthermore, excellent photoelectric conversion efficiency can be achieved without using a sensitizer like a titania solar cell.

  Further, according to the production method of the present invention, each constituent layer of the charge transfer type heterojunction structure can be formed without difficulty, and the identification of the fullerene polymer film is particularly performed by the Raman method and the Negzaphs method. It is possible to perform various evaluations from the fullerene polymer film structure to its degree of polymerization, amorphization, oxidation, and dielectric breakdown due to high voltage application in a non-destructive and accurate manner. It becomes. Since the fullerene polymer film can be accurately identified based on the evaluation results of such a fullerene polymer film, the target heterojunction structure can be reliably produced and can be used for controlling the physical properties thereof.

  In the heterojunction structure of the present invention, an electron-donating conductive organic film and an electron-accepting fullerene polymer film are laminated between a pair of electrodes having at least one light-transmitting property. Photoinduced charge transfer is possible, and it is suitable for solar cells and light emitting diodes. In that case, compared with the case where a fullerene vapor-deposited film is used as a constituent material, the durability and the electronic properties are further improved.

  In particular, when applied to a solar cell, an economical solar cell can be obtained compared to a conventional silicon pn junction solar cell, and the light weight and flexibility are remarkably excellent, and the energy conversion efficiency is There is no inferiority, and excellent photoelectric conversion efficiency can be achieved without using a sensitizer as compared with a titania solar cell.

  Further, according to the production method of the present invention, each of the constituent layers of the heterojunction structure can be formed without difficulty, and the fullerene polymer film can be identified particularly by the combined use of the Raman method and the Negzaphs method. Can be done. Moreover, various evaluations ranging from the structure of fullerene polymer film to its degree of polymerization, amorphization, oxidation, and dielectric breakdown due to high voltage application can be performed nondestructively and accurately. Can be used to control the fabrication conditions (and hence the physical properties) of the heterojunction structure.

The heterojunction structure of this invention is illustrated, Comprising: (A) is a simple heterostructure, (B) is each schematic sectional drawing of a double heterostructure. FIG. 2 is a diagram illustrating another simple heterojunction structure, in which (C) is a schematic cross-sectional view of a simple heterostructure and (D) is a double heterostructure. (A) schematic diagram showing the molecular structure of C ₆₀ is, (B) is a schematic diagram showing the molecular structure of C _70. Is a diagram illustrating a dimeric structure of the C ₆₀ molecules is thought to occur in the process of generating fullerene polymer. Is a diagram illustrating another dimeric structure of C ₆₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₂₀ (b)] other of C ₆₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₂₀ (c)] other of C ₆₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₂₀ (d)] other of C ₆₀ molecules is thought to occur in the process of generating fullerene polymer. It is a figure which shows the structure of _C118 molecule _| numerator considered to arise in the production | generation process of a fullerene polymer. It is a figure which shows the structure of _C116 molecule _| numerator considered to arise in the production | generation process of a fullerene polymer. Is a diagram illustrating the numbering system of C ₇₀ molecules. Is a diagram illustrating a dimeric structure of the C ₇₀ molecules is thought to occur in the course of the fullerene polymer. It is a figure which shows the other dimer structure of C70 molecule | numerator considered to arise in the process of a fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (a)] of the C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (b)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (c)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (d)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (e)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (f)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (g)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₄₀ (h)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The other dimeric structure of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer [C ₁₄₀ (i): is a diagram showing a D _2h symmetry). The diagrams showing the dimeric structure [C ₁₃₆ (a)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₃₆ (b)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₃₆ (c)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₃₆ (d)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₃₆ (e)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₃₆ (f)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. The diagrams showing the dimeric structure [C ₁₃₆ (g)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. It is a figure which shows the other dimer structure [ _C136 (h)] of C70 molecule | numerator considered to be produced in the production | generation process of a fullerene polymer. The diagrams showing the dimeric structure [C ₁₃₆ (i)] other of C ₇₀ molecules is thought to occur in the process of generating fullerene polymer. It is a figure which shows an example of the structure of a _C60 polymer. It is a figure which shows an example of the structure of a _C60 polymer film. It is a diagram showing a structure of a C ₆₀ vapor-deposited film. It is a figure which shows the manufacturing apparatus of fullerene molecule | numerator by arc discharge. It is a figure which shows the manufacturing apparatus of the fullerene polymer film | membrane by a plasma polymerization method. It is a figure which shows the manufacturing apparatus of a fullerene polymer film | membrane by a microwave polymerization method. It is a figure which shows the manufacturing apparatus of a fullerene polymer film | membrane by an electropolymerization method. The electron and hole movement state in the heterojunction part of the heterojunction structure of this invention is shown, (A) is a case where a step does not exist, (B) is a case where a step exists. It is a figure which shows the Raman spectrum of amorphous carbon. It is a figure which shows the Fermi level of an ITO thin film. It is a figure which shows the PES measurement result of a polythiophene thin film. It is a figure which shows the diode characteristic of a polythiophene thin film. Raman spectroscopic measurements of C ₆₀ polymer film is a graph showing by comparison with that of the graphite-like carbon. Is a diagram showing photoemission measurements of fullerene thin film (C ₆₀ polymer film and C ₆₀ vapor-deposited film). It is a figure which shows the band structure of an example of the heterojunction structure of this invention. It is a figure which shows the VI characteristic etc. of a heterojunction structure similarly. It is a figure which shows VI characteristic etc. of the other heterojunction structure of this invention. It is a figure which shows VI characteristic of the laminated body which excluded the formation of the conductive polymer film from the heterojunction structure, and changed the material of the counter electrode. It is a figure which shows the VI characteristic of the laminated body which changed the material of the counter electrode of a laminated body similarly. It is a diagram showing a Raman spectrum of the C ₆₀ polymer film obtained by a plasma polymerization method. Same, obtained by changing the conditions of the plasma polymerization method is a diagram showing a Raman spectrum of the C ₆₀ polymer film. It is a diagram showing a Raman spectrum of the C ₆₀ vapor-deposited film. It is a figure which shows the Raman spectrum of graphite-like carbon. A C ₆₀ polymer film was formed into a film with an argon plasma polymerization method, the C ₆₀ polymer film was formed into a film by electrolytic polymerization method is a diagram showing a Raman spectrum. Under constant pressure, when changing the plasma power, it is a diagram showing a Raman spectrum of the C ₆₀ polymer film was formed into a film by a plasma polymerization method. The plasma power is constant, when changing the pressure, is a diagram showing a Raman spectrum of the C ₆₀ polymer film was formed into a film by a plasma method. It is a diagram showing a Raman spectrum of the C ₆₀ vapor-deposited film obtained under constant pressure. It is a diagram showing a Raman spectrum of the C ₆₀ vapor-deposited film when changing the pressure. It is a figure which shows the Raman spectrum of the same _C60 vapor deposition film which changed the pressure further. Changing the pressure, it is a diagram showing a Raman spectrum of the C ₆₀ polymer film obtained by carrying out plasma polymerization method under a constant power. It is a diagram showing a Raman spectrum of the C ₆₀ polymer film when changing the plasma power. It is a diagram illustrating a Negu The Hus spectrum of C ₆₀ vapor-deposited film. It is a diagram illustrating a Negu The Hus spectrum of C ₆₀ plasma polymer film. FIG. 66 is an enlarged view showing a transition portion to a π antibonding orbital for each sample in FIGS. 63 and 64. FIG. ₅₃ is a diagram showing a Negaffus spectrum of a C ₆₀ polymer film of the sample of FIG. FIG. 66 is a diagram showing a Negaffus spectrum of an oxygen K edge of the carbon thin film of the sample of FIG. 66. In the heterojunction structure of this invention, it is a figure which shows the relationship between the spectrum by the Negafus method of a fullerene polymer film, and the orbital transition of an electron and a hole by light induction. It is a figure which shows VI characteristic etc. of the heterojunction structure of this invention which interposed the active layer between the conductive polymer film and the fullerene polymer film. It is a figure which shows the photoelectron emission spectrum of a phthalocyanine film | membrane. It is a figure which shows the relationship between the photoelectron energy of a film | membrane, and an absorption coefficient similarly. FIG. 70 is a diagram illustrating VI characteristics when the counter electrode is changed in the heterojunction structure of FIG. 69. ITO- is a diagram showing the VI characteristics of tetrathiafulvalene -C ₆₀ comprising a polymer laminate. It is a figure which shows the VI characteristic of the other heterojunction structure of this invention.

  In the charge transfer type heterojunction structure of the present invention, the fullerene polymer film is preferably in contact with the counter electrode in the laminated structure.

  In addition, including such a case, it is preferable that an active layer is interposed as a carrier generation layer between the fullerene polymer film and the conductive organic film.

  Moreover, in this invention, a board | substrate can be suitably provided in the outer surface side (surface exposed to air | atmosphere) of each electrode.

  As a typical heterojunction structure of the present invention, as shown in FIG. 1A, ITO (Indium tin oxide) is doped with tin on a transparent substrate 1 made of silicon, glass or the like. Light-transmitting electrode 2, conductive polymer film 3 such as polythiophene, fullerene polymer film 4 forming a heterojunction with this conductive polymer film, and counter electrode 5 made of aluminum or the like. The layers are preferably laminated in this order. Further, as shown in FIG. 1B, an active layer 6 such as carbon nanotube or phthalocyanine is interposed as a carrier generation layer between the conductive polymer film 3 and the fullerene polymer film 4. preferable. Here, each thickness of the conductive polymer film 3, the active layer 6, and the fullerene polymer film 4 may be 0.1 to 50 nm (preferably 5 to 20 nm) (hereinafter the same).

  However, as shown in FIGS. 2C and 2D, a heterojunction structure in which the conductive polymer film 3 and the fullerene polymer film 4 are interchanged with each other can also perform charge transfer, and is included in the scope of the present invention. It is.

  The conductive organic film preferably has an electron donating property and is preferably formed of a P-type conductive polymer containing a conjugated π electron system. Some preferred specific examples thereof include polyvinyl carbazole, poly (p-phenylene) -vinylene, polyaniline, polyethylene oxide, polyvinyl pyridine, polyvinyl alcohol, polythiophene, polyfluorene and polyparaphenylene, and derivatives of these constituent monomers. There is a polymer consisting of

  In addition, in order to control the electroconductivity, this conductive organic film may be added with a known dopant such as sulfate radical.

The fullerene polymer film functions as an electron-accepting thin film and is preferably composed of a C ₆₀ polymer and / or a C ₇₀ polymer, such as those shown in FIGS. 4 to 10 and FIGS. 32 and FIG. 33 are exemplified. However, it is not necessary to limit to these polymers so that it may mention later. This fullerene polymer film is characterized in that the fullerene molecules are closely bonded by covalent bonds as compared with the fullerene vapor deposition film shown in FIG.

  The active layer preferably provided is a carrier generation layer, and the material thereof includes a dye having a π electron system, a metal complex, a conductive polymer, a fullerene molecule, and a chemically modified derivative thereof, a single layer, Examples thereof include simple substances such as multi-walled carbon nanotubes or composites. Examples of the dye include a cyanine dye, phthalocyanine and a metal complex thereof, or porphyrin and a metal complex thereof.

  As the material of the light transmissive electrode, ITO (indium oxide doped with tin) is generally preferable, but thin films such as gold, silver, platinum, and nickel can also be used.

  Further, the material of the counter electrode includes one kind of metal such as aluminum, magnesium and indium or an alloy thereof, or ITO.

  On the other hand, the manufacturing method of the present invention for producing the charge transfer heterojunction structure basically includes a light transmissive electrode forming step, a conductive organic film forming step, a fullerene polymer film forming step, and a counter electrode. However, it is not necessarily limited to the order of these steps. However, it is necessary to form another constituent layer after identifying the fullerene polymer film. Furthermore, a step of attaching a substrate to the light transmissive electrode or the counter electrode, a step of interposing an active layer, or the like is added as necessary.

  The identification is most preferably performed by using both the Raman method and the Negzaphs method, both of which are non-destructive spectroscopy. Absence of either of these is insufficient as an identification method.

  Specific work of identification includes evaluation of the structure of fullerene polymer, degree of polymerization, amorphization, oxidation, and dielectric breakdown due to application of high voltage. The result of these evaluations is only identification of fullerene polymer film. However, it can be used for controlling the physical properties of the polymer film such as controlling the polymerization conditions.

  In the step of forming the light-transmitting electrode, it is common to form the electrode on the substrate rather than forming the electrode alone. The electrode material such as ITO described above is deposited on the substrate such as vapor deposition and sputtering. A film is formed using a technique.

  When using a thin film of another material, for example, a stable metal material such as gold, instead of ITO, it is important to form a thin film on the substrate to ensure light transmittance. The shape and pattern of the light transmissive electrode can be freely devised by a mask or other known means.

  The conductive organic film (or fullerene polymer film) is formed on the light transmissive electrode (in the case where the fullerene polymer film is formed on the light transmissive electrode, the conductive organic film is used). (The explanation is omitted below.)

  In this forming step, a vapor-deposited film or plasma polymer film of an organic low molecular compound having electron donating properties is formed on the light transmissive electrode.

  That is, when a high molecular weight monomer or a low molecular weight organic compound containing π electrons is vaporized and the gas is irradiated with relatively low energy high frequency plasma, ultraviolet rays, or an electron beam, a conductive property is formed on the transparent electrode. An organic film can be formed.

Such a π-conjugated organic low-molecular vapor-deposited film or plasma polymerized film has a conductivity of at least about 10 ⁻⁹ S / cm. Further, since the fullerene polymer film described later functions as an electron-accepting thin film, the organic low-molecular vapor-deposited film and the plasma polymer film described here need to function as an electron-donating thin film.

  Specific examples of the low molecular organic compounds include π-conjugated low molecules such as ethylene and acetylene, catacondensed organic compounds such as benzene, naphthalene and anthracene, pericondensed aromatic compounds such as perylene and coronene, or these compounds And heteroatom derivatives such as nitrogen, oxygen and sulfur. In addition, for example, oxygen, sulfur, selenium, tellurium and the like can be incorporated as heteroatoms in the organic skeleton system, but these elements normally supply two electrons to the π-conjugated system. Examples of the heterocyclic compound of oxygen or sulfur used as the system include furan and thiophene. In addition, when one of these elements is incorporated into a 6-membered ring or when two are incorporated into a 5-membered ring, the π electron system is excessively present according to the 4n + 2 rule, and thus a strong electron-donating compound. It becomes. For example, tetrathiafulvalene is a typical example of such a strong electron donating compound. Such a thin film or plasma polymer film of an organic compound having a strong electron donating property can form a heterojunction with an electron accepting fullerene polymer film, which will be described later, to cause more effective photoinduced charge transfer. it can.

  The material for forming the conductive organic film will be described with reference to specific examples of the polymer. In addition to the above-mentioned polyvinyl carbazole and polythiophene, the following polymer substances or derivatives thereof can be used. Can also be used in combination.

  That is, poly (3-alkylthiophene), poly [2-methoxy-5- (2′-ethylhexoxy) -p-phenylene] -vinylene, poly [2-methoxy-5- (2′-ethylhexoxy) -1,4 -Paraphenylene vinylene, poly (3-alkylthiophene), poly (9,9-dialkylfluorene), polyparaphenylene, poly (2,5-diheptyloxy-1,4-phenylene), polyphenylene, polyaniline, poly (p- Phenylene), polyethylene oxide, poly (2-vinylpyridine), poly (vinyl alcohol), and the like. Highly conductive organic thin films are polymerized by irradiation with relatively low energy high-frequency plasma, ultraviolet rays, X-rays, electron beams, etc. in a gas atmosphere of monomers of these polymer compounds or organic compounds containing a π-electron system. It is also possible to form

  Next, a fullerene polymer film is formed on the conductive organic film formed as described above as follows.

First, C ₆₀ , C ₇₀ , and higher order fullerene can be used as the fullerene molecule as a raw material, and these can be used alone or as a mixture of two or more. Particularly preferred are the aforementioned C ₆₀ fullerenes, C ₇₀ fullerenes, or mixtures thereof, which further include higher order fullerenes such as C ₇₀ , C ₇₈ , C ₈₀ , C ₈₂ and C _84. May be.

  These fullerene molecules can be produced by, for example, an arc discharge method of a carbon electrode using an apparatus as shown in FIG.

  In the reaction vessel 8 of this apparatus, a pair of carbon electrodes connected to an AC or DC power source 9, for example, counter electrodes 10a and 10b made of graphite are attached. First, after degassing the inside of the reaction vessel 8 from the exhaust port 11b with a vacuum pump, a low-pressure inert gas (helium, argon, etc.) is introduced from the introduction port 11a to fill the reaction vessel 8.

  Then, the ends of the counter electrodes 10a and 10b are opposed to each other through a gap, a predetermined current and voltage are applied from the DC power supply 9, and the ends of the counter electrodes 10a and 10b are brought into an arc discharge state for a predetermined time. maintain.

  Due to the arc discharge, the counter electrodes 10 a and 10 b are vaporized, and soot is gradually attached on the substrate 12 attached to the inner wall surface of the reaction vessel 8. When the adhesion amount increases, the reaction vessel 8 is cooled and the substrate 12 is taken out or the soot is collected by using a vacuum cleaner or the like.

This soot contains various fullerene molecules including C ₆₀ and C _70, and may contain about 10% or more fullerene molecules depending on conditions.

Fullerenes such as C ₆₀ and C ₇₀ can be extracted from this soot using a π-electron solvent such as toluene, benzene, or carbon disulfide. The fullerene obtained through this stage is called crude fullerene, and when it is further subjected to, for example, column chromatography, C ₆₀ and C ₇₀ can be separated and purified as simple substances.

  The fullerene molecules thus obtained serve as a raw material when forming a fullerene polymer. Examples of the polymerization method or film forming method include the following photopolymerization method, electron beam irradiation method, plasma polymerization method, microwave polymerization method and electrolytic polymerization method.

Photopolymerization method:
This polymerization method uses a heating device such as resistance heating that vaporizes fullerene molecules as an apparatus and an irradiation device that irradiates light such as ultraviolet rays through a window, and irradiates ultraviolet light while depositing fullerenes. By continuing for a certain time, a fullerene polymer film is formed on the substrate. At this time, fullerene molecules are excited by light and polymerize through this excited state.

  In addition, polymerization does not occur in the process of vapor deposition as described above, but once the vapor deposition film is formed and then irradiated with ultraviolet rays or the like, polymerization occurs. In this case, only the surface layer of the film is polymerized, and the inside of the film is polymerized. However, it should be noted (even in the experiment by the present inventors, it has been observed with a microscope that a cracked pattern can occur on the surface of the fullerene deposited film by irradiation with ultraviolet rays).

Electron beam irradiation method:
This uses an electron beam emitted from an electron gun instead of the light such as ultraviolet rays. The principle of polymerization is the same as in the photopolymerization method, and fullerene molecules are excited by an electron beam and polymerize through this excited state.

Plasma polymerization method:
There are a high-frequency plasma method, a direct-current plasma method, an ECR plasma method, and the like. Here, a high-frequency plasma method having a high degree of spread will be described with reference to the drawings.

  FIG. 36 shows a high-frequency plasma polymerization apparatus, in which a pair of electrodes 14a and 14b are arranged opposite to each other in a vacuum vessel 13, and these are connected to an external high-frequency power source 15, and fullerene is placed on one electrode 14b. A substrate 16 for attaching a polymer film (that is, a substrate on which the conductive polymer film is formed on a light transmitting electrode) 16 is set.

  Further, a container 17 such as a molybdenum boat for storing the fullerene molecules as a raw material is disposed in the vacuum container 13, and this is connected to an external resistance heating power source 18.

  In the polymerization apparatus having such a structure, first, for example, a low-pressure inert gas (argon or the like) is supplied from the introduction port 19 into the vacuum vessel 13 deaerated from the exhaust port 20, and the vessel is filled with the same gas before the vessel is filled. 17 is energized and heated to vaporize the fullerene molecules therein. When a high-frequency voltage is applied from the high-frequency power source 15 to generate high-frequency plasma between the electrodes and the fullerene gas is irradiated, a fullerene polymer film holding a π-electron skeleton can be formed on the substrate 16. it can.

  The high-frequency power source 15 may be replaced with a DC power source (DC plasma method), or when the container 17 is heated without driving these power sources (thus generating no plasma), the fullerene is not polymerized. The deposited film is formed on the substrate 16.

  If the temperature of the substrate 16 is too high, the adhesion amount of the fullerene polymer film is lowered. Therefore, it is usually kept at 300 ° C. or less, and if the plasma power is about 100 W, it hardly exceeds 70 ° C.

  FIG. 37 shows a microwave polymerization apparatus. This includes a vessel 21 such as a molybdenum boat that contains fullerene molecules as a raw material supply source, a microwave action unit 23 that causes the microwave 22 to act on the fullerene molecules that are vaporized and fly from the vessel 21, and induction by the microwave 22 ( A fullerene polymer is generated by excitation and non-equilibrium plasma), and a reaction chamber 25 for forming a fullerene polymer on a gas 24 and a microwave generator for generating the microwave 22 are formed.

  A gas introduction pipe 26 for introducing a carrier gas such as argon gas into the apparatus is opened on the inner wall of the polymerization apparatus near the container 21. This carrier gas 27 not only has a carrier ability to accompany fullerene molecules 28 and guide them onto the substrate 24 in the reaction chamber 25, but also has the ability to modify the surface of the substrate 24 as follows. Yes.

  That is, before supplying the fullerene molecule 28 into the apparatus, the carrier gas 27 was first introduced, and excited by the microwave action unit 23 and bombarded on the surface of the substrate 24 in the reaction chamber 25. The surface of the substrate 24 is etched by the carrier gas 27, and the adhesion or adhesion with the fullerene polymer film adhering to the surface is improved.

  The microwave generator (microwave unit) has a structure in which a microwave oscillation source 29, an isolator 30, a power meter 31, a sli tab tuner 32, and a reflection cavity 34 are connected by a waveguide 35. . Among these components, the microwave oscillation source 29 is composed of an oscillation source such as a magnetron, the isolator 30 has a microwave rectification capability, the power meter 31 has a microwave power detection capability, and a three stub. The tuner 32 adjusts the number of oscillations of the microwave and has a matching capability, and the reflection cavity 34 reflects the microwave and matches the wavelength, thereby making the microwave in the microwave action unit 23 a stationary wave. It is a device for.

  The reaction chamber 25 can be configured to have a larger diameter than the resonance tube 36 that is a flow path of the carrier gas 27 and the fullerene molecules 28, and the fullerene efficiently and densely induced by the microwave action portion 23 of the resonance tube 36. Molecules are guided onto a substrate 24 such as silicon provided on a support (not shown), and a fullerene polymer film can be uniformly formed thereon. The reaction chamber 25 is provided with an evacuation system 37 so that the inside of the reaction chamber 25 can be maintained at a predetermined pressure.

  The support to which the substrate 24 is attached may be conductive or insulating, and may be provided with a heating means (such as an energizing means).

  When using such a microwave polymerization apparatus, first, the inside of the reaction chamber 25 is held at, for example, about 0.05 to 1 Torr with argon gas, and the container 21 is heated by heating means to vaporize fullerene molecules therein. . Then, this is irradiated with high-frequency plasma of, for example, about 13 or 56 MHz by the microwave action unit 23. In this way, fullerene molecules are excited and a fullerene polymer film is formed on the substrate 24.

  The temperature of the substrate 24 may normally be 300 ° C. or lower. If the temperature exceeds 300 ° C., the amount of fullerene polymer film attached may decrease (when a bias is applied, the fullerene polymer film tends to adhere). No special control is required to maintain the temperature of the substrate 24 during film formation in the normal range. For example, if the power of the microwave is about 100 W, the temperature hardly exceeds 100 ° C. However, if the substrate 24 is placed on the microwave action part 23, the temperature may rise to around 1000 ° C.

Electropolymerization method:
FIG. 38 shows an electrolytic polymerization apparatus. The electrolytic cell 38 is provided with an electrode 39 as an anode and an electrode 40 as a cathode connected to a potential stat 41, and a reference electrode 42 is also provided on the potentiostat 41. They are connected so that a predetermined electric potential is applied between the electrodes 39 and 40.

  Further, the electrolytic cell 38 is provided with a gas introduction pipe 45 for introducing inert gas 44 in order to remove oxygen gas and the like from the non-aqueous solvent 43. Further, a magnet neck stirrer 46 for moving a stirrer (not shown) in the cell is attached to the lower part of the electrolysis cell 38.

  In order to operate the electropolymerization apparatus having such a structure, a fullerene molecule as a raw material, a supporting electrolyte for promoting electrolysis, and a nonaqueous solvent 43 are charged in an electrolytic cell 38, and a potentiostat 41 is provided. In operation, predetermined electrical energy is applied between the electrodes 39 and 40. Then, the fullerene molecule becomes an anion radical, and the fullerene polymer is formed on the negative electrode 40 as a thin film and / or a precipitate. The spherical fullerene polymer obtained as a precipitate can be easily recovered by means such as filtration and drying, and after recovery, it is hardened or kneaded into a resin to form a thin film. Can be formed.

  The electrodes 39 and 40 are preferably metal electrodes, but may be formed of other conductive materials, and those obtained by vapor-depositing a conductive material such as metal on a substrate such as glass or silicon are used. May be. The material of the reference electrode 42 also depends on the supporting electrolyte, but need not be limited to a specific metal.

  Removal of oxygen or the like by the inert gas 44 can be normally performed by bubbling of helium gas, but other inert gas such as nitrogen or argon may be used instead of the helium gas. In order to thoroughly remove oxygen and the like, a dehydrating agent is used in advance before electrolysis, vacuum deaeration is performed, each solvent is stored in an ampule, and introduced into the electrolytic cell 38 through a vacuum line. Good.

  In any case, oxygen and the like are removed from the electrolyte solution by preventing oxygen and the like from being taken into the fullerene polymer film and suppressing the expression of paramagnetic centers, thereby stabilizing the fullerene polymer film. It is none other than to improve sex.

Examples of the supporting electrolyte include tetrabutylammonium perchlorate, lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), sodium peroxide (NaClO ₄ ), LiCF ₃ SO ₃ , lithium hexafluoroacese. Knight (LiAsF ₆ ) or the like can be used, but when these supporting electrolytes are used, the resulting spherical carbon polymer often precipitates in the electrolyte solution.

On the other hand, for example, when lithium perchlorate (LiClO ₄ ) or tert-butylammonium perchlorate salt is used, a spherical carbon polymer is obtained as a thin film on the electrode, depending on the temperature during the electropolymerization reaction. be able to.

  In the present invention, it is desirable to use a mixed solvent of a first solvent that dissolves fullerene molecules and a second solvent that dissolves the supporting electrolyte as the non-aqueous solvent. The mixing ratio is desirably the first solvent: second solvent = 1: 10 to 10: 1 (volume ratio).

As the first solvent, it is preferable to use a low-polarity solvent having a π-electron system (low-polarity solvent), for example, selected from the group consisting of carbon disulfide (CS ₂ ), toluene, benzene, and orthodichlorobenzene. And at least one kind of solvent.

  Further, as the second solvent, it is preferable to use a solvent having a high polarity and a large dielectric constant. For example, at least one solvent selected from the group consisting of acetonitrile, dimethylformamide, dimethylsulfoxide, and dimethylacetamide is used. Can be mentioned. Of these, acetonitrile is particularly preferable.

  In general, fullerene molecules are soluble only in the low-polarity solvent such as carbon disulfide, and the solubility in an aliphatic solvent such as n-hexane is extremely low. Of course, it does not dissolve in a polar solvent, and this is the biggest problem when performing electropolymerization of fullerene molecules.

  This is because the supporting electrolyte usually used in electrolytic polymerization is soluble only in a polar solvent such as water.

  In order to perform electropolymerization of fullerene molecules, it is necessary to select a solvent that can dissolve both fullerene molecules and the supporting electrolyte at the same time, but there is no single solvent that satisfies this condition. At least a mixed solvent composed of individual solvents each having the above-mentioned dissolution performance is required.

  However, as long as it is such a mixed solvent, what is necessary is not necessarily the case. By simply using such a mixed solvent, the solubility of either the fullerene molecule or the supporting electrolyte or both is often insufficient.

  For example, water-based solvents such as water are generally known as good solvents for supporting electrolytes that are salts, but are not sufficiently soluble with low-polarity solvents that can dissolve fullerene molecules, so a mixed solvent composed of both is preferable. It can not be said.

  According to the inventor's research, the preferred mixed solvent used in the present invention is composed of a first solvent and a second solvent. Among these, a low polarity solvent is used as the first solvent, and polarity is used as the second solvent. It is desirable to use an organic solvent having a high dielectric constant and a high dielectric constant.

  Specific examples of the second solvent are as described above, and most suitable is acetonitrile. Acetonitrile is a solvent often used in preparing organic radicals in the presence of a supporting electrolyte in an electrolytic cell.

  However, in the present invention, it is not necessary to specifically limit the second solvent to this acetonitrile, and as described above, dimethylformamide and other solvents are also preferable for achieving the object of the present invention.

  The fullerene polymer thin film obtained by the above method is a gold film formed on a silicon or glass substrate by vapor deposition or sputtering, on a single substrate such as silicon or glass, on a transparent electric billion substrate such as ITO, A film is formed on a metal substrate such as platinum or aluminum. Alternatively, the film may be formed on a so-called comb-shaped electrode in which gold, platinum, aluminum, or the like is deposited or sputtered in a comb shape using a mask. Furthermore, a sandwich structure sandwiched between so-called electrodes may be used. In order to obtain such a structure, a fullerene polymer is formed in a desired thickness on a metal electrode formed on a glass or silicon substrate or on a transparent electrode such as ITO, A mask is placed on the fullerene polymer film, and a metal layer such as gold, platinum or aluminum or a transparent conductor layer such as ITO may be formed by a technique such as sputtering or vapor deposition.

  As described above, since the molecular structure of fullerene partially remains on the surface of the fullerene polymer film obtained by various polymerization methods, a large number of double bonds exist. Therefore, surface modification (surface treatment) can be performed by various methods.

  For example, fullerene polymer under the atmosphere of hydrocarbon gas such as acetylene, methane, ethane, propane, butane, toluene, benzene, acetone, acetonitrile, ethanol, methanol, and gas such as oxygen, hydrogen, chlorine, fluorine The film can be surface modified using techniques such as microwave induction, direct current plasma, alternating current plasma, or the fullerene polymer film can be surface modified using a metal complex or an organic radical in solution. it can.

  Such surface modification is effective for modifying the fullerene polymer film or imparting its specificity to the purpose and application.

Incidentally, fullerene polymer films, particularly fullerene polymer films obtained by microwave polymerization, have a dangling spin problem. For example, when C ₆₀ and / or C ₇₀ are used as raw materials, the power is set to 100 W to several hundred W, and microwave polymerization is performed at room temperature, a fullerene polymer film containing dangling spins of about 10 ¹⁸ spings / g is obtained. It is done.

  This dangling spin has a great influence on the electrical conductivity and band structure of the fullerene polymer film or the temporal stability of physical properties.

  This dangling spin is thought to be due to the fact that the ideal cross-link structure was not formed, but its content can adjust the temperature of the substrate for attaching the fullerene polymer film, It can be reduced to some extent by exposure to an atmosphere such as hydrogen plasma after film formation. The process of the decrease can be confirmed from the difference in absorption intensity by the electron spin resonance method.

  In addition, with respect to a laminate composed of a light transmissive electrode-conductive polymer film-fullerene polymer film (or light transmissive electrode-fullerene polymer film-conductive polymer film) obtained through each of the above steps. In the present invention, it is necessary to form a counter electrode as a further process.

  This counter electrode is made of, for example, an oxide such as ITO, a metal such as aluminum, magnesium, or indium, or an alloy composed of two or more of these metals, such as vapor deposition, sputtering, electron gun, and electrolytic plating. A thin film can be formed on the fullerene polymer film using a technique.

  In the heterojunction structure of the present invention thus obtained, an electron-donating conductive polymer and an electron-accepting fullerene polymer film are laminated between electrodes. Is possible. Furthermore, if the junction with the conductive electrode is an ohmic junction on both sides of the heterojunction thin film and there is no step in the energy band at the heterojunction, as shown in FIG. When it has a step in the energy band as shown in the same figure (B), it becomes smooth and functions as a solar cell. Since electrons and holes are recombined there to generate light, it functions as a light emitting diode. . The presence or absence of the step can be adjusted by devising the material of the laminate between the electrodes described above.

  In the present invention, it is important to form other constituent layers after identifying the fullerene polymer film in the step of forming each layer of the heterojunction structure.

  That is, by examining the fullerene polymer film spectroscopically using, in particular, the Raman method and the Negzafus method, knowledge on its structure, degree of polymerization, amorphization, oxidation, dielectric breakdown due to application of high voltage, etc. is obtained. .

  In general, Raman spectroscopy is often used in spectroscopic studies of carbon thin films. This is a vibration analysis method based on the change in polarizability caused by electromagnetic wave irradiation. This is often used because carbon materials generally absorb infrared light and are difficult to measure. As an example, FIG. 40 shows a Raman spectrum of amorphous carbon obtained by a relatively low temperature CVD method. The excitation source is 514.5 nm of an argon ion laser.

  The spectrum of FIG. 40 reflects the characteristics of the amorphous carbon thin film, although the line width is large and small, and two characteristic bands are observed around 1350 and 1600 cm-1, respectively. is called.

  If a fullerene polymer film is formed and the above Raman spectrum is obtained, it is presumed that the structure has changed to an amorphous carbon structure rather than a fullerene polymer. Further, when a band of 1350 cm is observed, it can be predicted that the cross-link structure between molecules is insufficient or that many dangling structures exist.

In general, the Raman spectrum of a C ₆₀ polymer having a periodic structure is known to have many characteristic bands [T. Wagberg, et al., Appl Phys. A, 64.223 (1997), (AMRao et al., Phys. Rev. B, 55, 4766 (1997))

  However, regarding the Raman spectrum of a randomly connected polymer obtained by a plasma polymerization method, an electrolytic polymerization method, or the like, no clear criteria have been shown so far.

  On the other hand, the Negzaphus spectrum is the observation of the transition from the core electrons (1s electrons) of the carbon atoms forming the carbon thin film to the vacant orbit. It has been used for evaluation.

  The present inventor was able to find out that the fullerene polymer that could not be realized so far could be more accurately identified only by the combined use of the Raman method and the Negzafus method.

  Hereinafter, the present invention will be described more specifically based on embodiments. However, the present invention is not limited to the following embodiments.

Example 1 (Measurement of Fermi level of light transmissive electrode (ITO thin film))
An ITO thin film is formed on a commercially available quartz glass by sputtering to form a light-transmitting electrode, its photoelectron emission spectroscopy (PES) is measured, and the Fermi surface level of the ITO thin film is measured. Evaluated. The result is shown in FIG.

  From this measurement result, it became clear that the Fermi level of the ITO thin film exists at 4.87 eV under the vacuum level.

Example 2 (Formation of polythiophene thin film (conductive organic film) and measurement of its properties)
Next, a commercially available polythiophene thin film (using sulfate radical as a dopant) was formed on the ITO film. The measurement result of PES of this polythiophene thin film is shown in FIG.

  From this measurement result, it is clear that the low electron band edge level of the polythiophene thin film exists at 4.82 eV under the vacuum level.

  A polythiophene thin film was formed on quartz glass, and the current-voltage (VI) characteristics were examined. FIG. 43 shows the measurement results of the VI characteristics and the number of absorption systems by photon energy.

  Polythiophene thin films were formed on the ITO thin film and the gold thin film, respectively. First, the Fermi level of ITO and gold was measured by a photoelectron emission method (Photoelectron Emission method), and the Fermi level of the polythiophene thin film was measured by a contact potential difference method based on this measurement value.

  As a result, the Fermi level of the polythiophene thin film formed on the ITO thin film was 4.4 eV, whereas that of the polythiophene thin film formed on the gold thin film showed almost the same value as 4.5 eV.

Example 3 (Film formation of fullerene polymer film and measurement of various physical properties)
Next, a fullerene polymer film was formed on the polythiophene thin film.

First, fullerene molecules as raw materials were prepared as follows. In an apparatus as shown in FIG. 35, a graphite rod having a diameter of 10 mm and a length of 35 cm is used as a positive electrode, and arc discharge is performed with a direct current of 150 amperes in an atmosphere of helium 100 Torr. Was obtained, the polarities of the two electrodes were reversed, and the deposits such as carbon nanotubes deposited on the original negative electrode were further vaporized to form soot. Soot accumulated in the water-cooled reaction vessel was collected with a vacuum cleaner and extracted with toluene to obtain crude fullerene. The crude fullerene was washed and dried with hexane, and then purified by vacuum sublimation. When the fullerene molecules thus obtained were subjected to time-of-flight mass spectrometry, C ₆₀ and C ₇₀ were contained at a ratio of about 9: 1.

<Microwave polymerization>
Next, in order to form a fullerene polymer film, the fullerene molecules were filled in a molybdenum boat and installed in a reaction tube portion of a microwave polymerization apparatus as shown in FIG. After sufficiently degassing the reaction chamber with a molecular turbo pump, the introduction of argon gas was started. When the inside of the reaction chamber became constant at 0.05 Torr, the microwave oscillating device was operated and the microwave power was adjusted to 400 W while adjusting with a tuner. When the microwave output became constant, the molybdenum boat was energized, and the temperature was raised by gradually increasing the current value. The vaporization deposition of fullerene was monitored by a quartz film thickness sensor installed beside the substrate. For confirmation, the thickness of the fullerene polymer film was measured using a contact-type film thickness meter. A nanoammeter was used for current measurement. The band gap of the fullerene polymer film was determined from the temperature dependence of the current value.

At the time of film formation, a glass substrate and a silicon substrate were also installed in the bell jar at the same time, and physical properties were measured. Mass spectrometry of the fullerene polymer film was performed using a time-of-flight mass spectrometer by ablation and ionization with a nitrogen pulse laser. The dangling spin was measured using an x-band electron spin resonance apparatus in a nitrogen atmosphere. Using a toluene solution of di-tert-butylnitroxide as a standard spin, the unit of fullerene polymer film is obtained by relative comparison of the third and fourth absorption lines from the low magnetic field of the digital manganese marker. The number of dangling spins per weight was determined. The results are as follows. In addition, the value of the band gap was obtained by the Forbidden-indirect method as a result of transmittance measurement.
Film thickness (contact film thickness meter): 30 nm
Electrical conductivity: 1.1 × 10 ⁻⁸ S / cm
Band gap: 1.4 eV
Dangling: 2.0 × 10 ¹⁸ spins / g

Next, instead of the vacuum sublimation, C ₆₀ was purified using a flash column filled with activated carbon filler, and a fullerene polymer film was formed under the same conditions using this as a raw material. The results of physical property evaluation are shown below.
Film thickness (contact film thickness meter): 30 nm
Electrical conductivity: 1.2 × 10 ⁻⁷ S / cm
Band gap: 1.5 eV
Dangling: 2.5 × 10 ¹⁸ spins / g

<Plasma polymerization>
The above was film formation by microwave polymerization, but next, a fullerene polymer film was formed by RF plasma (13.56 MHz) using an RF plasma polymerization apparatus as shown in FIG. The C ₆₀ purified housed in a molybdenum boat, vaporized by resistance heating, and polymerization was carried out at a power of 70 W. The same physical property evaluation was performed on the obtained fullerene polymer film. The results were as follows.
Film thickness (contact film thickness meter): 30 nm
Electrical conductivity: 1.8 × 10 ⁻⁷ S / cm
Band gap: 1.5 eV
Dangling: 2.0 × 10 ¹⁸ spins / g

  Further, when Raman spectroscopy was performed on the fullerene polymer films obtained by the microwave polymerization method and the plasma polymerization method, it was suggested that the polymerization structures of the two were almost the same.

Next, C ₆₀ was replaced with commercially available C ₇₀ as a raw material, and Ar plasma polymerization was performed in the same manner as described above. The result of physical property evaluation of the obtained fullerene polymer film is shown below.
Film thickness (contact film thickness meter): 45nm
Electrical conductivity: 1.0 × 10 ⁻⁸ S / cm
Band gap: 1.5 eV
Dangling: 7.8 × 10 ¹⁷ spins / g

When the Raman spectroscopic measurement result of the C ₆₀ polymer film was compared with that of graphite-like carbon, a so-called disorder band observed near 1350 cm −1 of amorphous carbon as shown in FIG. 44 was not observed. It was. The bands of 1460 and 1580 cm −1 are attributed to the target stretching vibration of a single bond C—C forming a 5-membered ring and the symmetrical stretching vibration of a weakly conjugated C═C double bond.

Next, in order to clarify the band structure of the fullerene thin film, the level of the valence band edge was evaluated from the photoelectron emission spectrum of the C ₆₀ polymer film obtained by the plasma polymerization method and the electrolytic polymerization method. The result is shown in FIG. For comparison, the case of a C ₆₀ vapor deposition film is also shown.

Example 4 (Preparation of heterojunction structure and its physical properties)
Next, with respect to the laminate forming the polythiophene film with C ₆₀ polymer film on the ITO electrode, further an aluminum electrode was formed as follows as a counter electrode. First, the vapor deposition machine was evacuated to 10 ⁻⁸ Torr by a turbo pump, and then high-purity hydrogen gas was backfiled. Aluminum was formed on the C ₆₀ polymer film of the above laminate in a hydrogen atmosphere of 10 ⁻⁵ Torr to obtain a heterojunction structure.

  FIG. 46 shows the band structure of the heterojunction structure obtained from the evaluation of the edge of the valence band by the photoelectron emission method, the Fermi level by the contact potential difference method, and the band gap by the optical method.

  In addition, the VI characteristics of this heterojunction structure were evaluated. The result is shown in FIG. In addition, it was confirmed whether or not it has characteristics as a photocell using a 500 W Xe lamp. As a result, when light was irradiated from the ITO side, a remarkable function as a photocell was confirmed as shown in the figure.

  Moreover, the VI characteristics were evaluated for the heterojunction structure having the same structure except that the aluminum was replaced with gold. The results are shown in FIG. This heterojunction structure also has a function as a photocell.

  For comparison, the relationship between operating temperature, voltage, and current was measured for a laminate in which the polythiophene film was omitted, indium and gold were used for the counter electrode, and ITO was used for the light transmissive electrode. Results as shown in 49 and 50 were obtained. In any case, it is understood that the desired VI physical properties cannot be obtained and the characteristics change depending on the temperature.

  Next, the Raman spectrum of each of the above fullerene polymer films was measured.

Example 5
In the above plasma polymerization, plasma polymerization of C ₆₀ was performed at an argon pressure of 0.1 Torr and a plasma power of 50 W. As a result of measuring the Raman spectrum of the obtained polymer film, a spectrum as shown in FIG. 51 was obtained. However, in this measurement, the power of the argon ion laser was suppressed to such an extent that no photo-induced structural change occurred.

Example 6
After irradiating the surface of the C ₆₀ polymer film formed in the same manner as in Example 5 with 200 W argon plasma for 2 hours, Raman measurement was performed with a laser beam having the same intensity as in Example 16. As a result, a Raman spectrum as shown in FIG. 52 was obtained.

Example 7
A vapor deposition film of C _{60 was formed} by a conventional method, and Raman measurement was performed with a laser beam having the same intensity as in Example 5. As a result, a Raman spectrum as shown in FIG. 53 was obtained.

Example 8
Raman measurement of commercially available graphite-like carbon was performed. The results are shown in FIG.

From the results of Raman measurement, the spectrum shown in FIG. 51 is a spectrum characterizing a randomly oriented C ₆₀ polymer. The peak at 1464 cm −1 is a single bond symmetrical stretching vibration, and the peak at 1571 cm −1 is double. It is attributed to the symmetric stretching vibration of connectivity. Further, the shoulder seen in the vicinity of 1425 cm −1 is attributed to the CC symmetric stretching vibration of the intermolecular bond. What is important here is that the peak at 1470 cm −1 called the Pentagonal Pinch Mode in the spectrum shown in FIG. 53 is the origin of the peak at 1464 cm −1 in FIG. 51 and is slightly shifted.

Furthermore, it was suggested that the spectrum of Example 6 was made amorphous by clearly observing a large Disorder Band. Although the width of the line is different, the peak position coincides with the spectrum of the graphite-like carbon shown in FIG. Thus, the spectrum profile as shown in FIG. 51 is unique to the C ₆₀ polymer.

FIG. 55 shows a C ₆₀ polymer film formed in 75 W argon plasma and a paper by the discoverers [P. Strasser, M. Ata, J. Phys. Chem. B, 102, 4131 (1998)]. Raman spectra of C ₆₀ polymer was formed into a film by electrolytic polymerization method shown in shown. Both the peak positions and the waves are in good agreement with FIG. 51, and peaks of 1464 and 1571 cm −1 are always observed for C ₆₀ randomly oriented polymers.

Example 9
Next, by changing the plasma power in various ways under a pressure of 0.1 Torr, per C ₆₀ polymer film was formed by plasma polymerization, it was subjected to Raman measurement. The result is shown in FIG.

In addition, using the same plasma polymerization method, Raman measurement was performed on the C ₆₀ polymer film formed by changing the pressure under a plasma power of 50 W in various ways. The result is shown in FIG.

Further, FIG 58 is under a pressure of 0.01 Torr, FIG. 59 under a pressure of 0.025Torr, results of Figure 60 are under a pressure of 0.2 Torr, in Raman measurements of C ₆₀ evaporated film was formed by each vapor deposition Show.

Further, a C ₆₀ polymer film was formed by plasma polymerization at a pressure of 0.1 Torr and a plasma power of 10 W, and the Raman measurement was performed. The result is shown in FIG. 61, and the result of Raman measurement of the C ₆₀ polymer film obtained in the same manner except that the plasma power was changed to 30 W is shown in FIG.

The above Raman shifts are summarized in Table 3 below.

  Next, the Negzafus method was evaluated.

Example 10
The K (K orbital) edge neg-affus spectrum of the C ₆₀ deposited film was measured. The results are shown in FIG.

Example 11
The K-edge Negaffus spectrum of the C ₆₀ plasma polymerized film obtained in Example 5 was measured. The results are shown in FIG.

FIG. 65 shows an enlarged view of the transition part to the π antibonding orbit of Examples 10 and 11. The assignment of eigenvalues based on semi-empirical levels of molecular orbital calculations and calculations performed with both MNDO / AM-1 and MNDO / PM-3 parameterizations is illustrated. In addition, the calculation result of the C ₆₀ dimer at the same level was predicted to decrease in the spectral intensity as the number of electrons that can be regarded as π electrons decreased, although orbital level dispersion occurred. The actual spectral pattern reproduces this well.

Example 12
Negzaf's measurement of the carbon thin film of Example 6 was performed and is shown in FIG. This pattern is completely different from Examples 10 and 11, and supports the progress of amorphization.

Example 13
The surface of the sample of Example 12 was treated with 50 W O ₂ plasma for 5 minutes, and NEZAFS measurement of oxygen K-Edge was performed. The results are shown in FIG. Originally, such a peak is not observed from the non-oxidized surface, so it can be inferred that strong plasma irradiation induced amorphization and further oxidation progressed in the atmosphere.

Table 4 below shows a comparison of the above-described Negzaphth measurement results at the valence band level.

  FIG. 68 shows the relationship between the above-described spectrum obtained by the Negzafus method and the corresponding orbital transition of electrons and holes caused by light induction.

Example 14
In the heterojunction structure composed of ITO electrode, polythiophene film, C ₆₀ polymer film and aluminum electrode (counter electrode) produced in Example 4, a phthalocyanine film (active layer) is placed between the polythiophene film and the C ₆₀ polymer film. A heterojunction structure using gold as a counter electrode was manufactured according to Example 4.

  The VI characteristic is shown in FIG. 69, and it can be seen that the photocell characteristic is good. Note that the measurement result of the photolectron emission spectrum of the phthalocyanine film is shown in FIG. 70, and the relationship between the photon energy and the absorption coefficient is shown in FIG.

Example 15
In the heterojunction structure composed of the ITO electrode, polythiophene film, C ₆₀ polymer film and aluminum electrode (counter electrode) produced in Example 4, a glass substrate is laminated on the outer surface (surface exposed to the atmosphere) of the ITO electrode; and , polythiophene film was manufactured in the C ₆₀ polymer film and each other permuted FIG 2 (c) how the such heterojunction structure shown pursuant to example 6.

  Although this heterojunction structure did not function sufficiently as a photocell, it can move charges and exhibits linear VI characteristics, so that it can be used for light quantity measurement and the like.

Example 16
Moreover, in the heterojunction structure of Example 14, a heterojunction structure using aluminum instead of gold as a counter electrode was manufactured according to Example 6, and its VI characteristics were measured. The result is shown in FIG. This figure shows that this heterojunction structure has a function as a photocell.

Example 17
First, 20 W of low plasma power argon plasma irradiation was performed while vaporizing tetrathiafulvalene molecules with a molybdenum resistance heater to form a film on the same ITO as in Example 1. In the same process, a thin film was formed on a glass substrate, and photoelectroemission and band gap were measured. As a result, the band gap was estimated to be 2.4 eV. The valence edge almost coincided with the Fermi level of ITO.

Furthermore, the Raman and infrared measurement results of the obtained tetrathiafulvalene suggested that the tetrathiafulvalene molecule had a dehydrogenated and polymerized structure. The conductivity was on the order of 10 ⁻⁴ to 10 ⁻² S / cm, although it was affected by the subtle conditions of the plasma.

Next, a fullerene polymer was formed on the tetrathiafulvalene thin film. First, fullerene molecules as raw materials were prepared as follows. In an apparatus as shown in FIG. 35, a graphite rod having a diameter of 10 mm and a length of 35 cm was used as a positive electrode, and arc discharge was performed with a direct current of 150 amperes under 100 Torr of helium. After the graphite rod was almost vaporized and soot containing fullerene was obtained, the polarities of the two electrodes were reversed to further vaporize deposits such as carbon nanotubes deposited on the original negative electrode to obtain soot. Soot accumulated in the water-cooled reaction tube was collected with a vacuum cleaner and extracted with toluene to obtain crude fullerene. After the resulting crude fullerenes were washed dried with hexane, to give only a C ₆₀ by flash column filled with activated carbon, further which was purified by vacuum sublimation.

  Next, a fullerene polymer film was formed. Fullerene molecules as raw materials were produced in the same manner as in the above example. This fullerene molecule was filled in a molybdenum boat and installed in a reaction tube site in a plasma polymerization apparatus. After sufficiently degassing with a molecular turbo pump, introduction of argon gas was started. When the inside of the reaction tube became constant at 0.05 Torr, the plasma oscillation device was operated to adjust the power to 50 W while performing matching adjustment. This was heated by energizing the molybdenum boat and gradually increasing the current value. The vaporization deposition of fullerene was monitored by a quartz film thickness sensor installed beside the substrate. For confirmation, the film thickness of the fullerene polymerized thin film was measured using a contact-type film thickness meter. A nanoammeter was used for current measurement. The band gap of fullerene polymer thin film was determined from the temperature dependence of the current value.

  At the time of film formation, a glass substrate and a silicon substrate were also installed in the bell jar at the same time, and physical properties were measured. Mass analysis of the fullerene polymer thin film was performed by a time-of-flight mass spectrometer by ablation and ionization with a nitrogen pulse laser. The dangling spin was measured using an x-band electron spin resonance apparatus in a nitrogen atmosphere. Using a toluene solution of di-tert-butylnitroxide as a standard spin, the unit of fullerene polymer film is obtained by relative comparison of the third and fourth absorption lines from the low magnetic field of the digital manganese marker. The number of dangling spins per weight was determined. The band gap value is obtained by measuring the transmittance measurement result by the Forbidden-indirect method.

These measurement results were the same as those in Example 3. Further, the Raman spectroscopic measurement of the C ₆₀ polymer film and the evaluation of the valence band edge level were the same as those shown in FIGS. Incidentally, the ITO- tetrathiafulvalene -C ₆₀ where the transmittance characteristics of the laminate comprising the polymer were measured, the results shown in FIG. 73 were obtained.

Next, an indium electrode was further installed as a counter electrode on the laminate in which the C ₆₀ polymer was formed on the tetrathiafulvalene film (conductive polymer) by plasma polymerization. First, the vapor deposition machine was evacuated to 10 ⁻⁸ Torr by a turbo pump, and then high-purity hydrogen gas was backfiled. An indium film was formed on the hetero thin film in a hydrogen atmosphere of 10 ⁻⁵ Torr. From the evaluation of the valence band edge by the photoelectron emission method, the Fermi level by the contact potential difference method, and the band gap by the optical method, the band structure of the obtained heterojunction structure is the same as that shown in FIG.

  In addition, the VI characteristics of this heterojunction structure were evaluated. In addition, it was confirmed whether or not it has characteristics as a photocell using a 500 W Xe lamp. As a result, when light was irradiated from the ITO side, a remarkable function as a photocell was confirmed.

Example 18
Further, a heterojunction structure having the same structure except that the indium was replaced with aluminum was manufactured, and the VI characteristics were measured. The results are shown in FIG. As is apparent from this, this heterojunction structure exhibits a function as a photocell.

Example 19
ITO electrodes fabricated in Example 17, tetrathiafulvalene layer, the heterojunction structure consisting of a C ₆₀ polymer film and an indium electrode, tetrathiafulvalene layer and C ₆₀ polymer film and a heterojunction structure interchanged with Manufactured. Although this heterojunction structure has a linear VI characteristic and does not function sufficiently as a photocell, charge transfer is possible.

  As is clear from the above, the heterojunction structure of the present invention is capable of photoinduced charge transfer and has a suitable application as a solar cell, a light emitting diode, or the like.

  In addition, it can be seen that the fullerene polymer can be accurately identified only by the combined use of the Raman method and the Negzafus method. Therefore, since it can be confirmed that the fullerene polymer film is surely formed and the next upper layer film forming process can be performed, the intended heterozygote can always be prepared. Moreover, when it is found that the degree of polymerization of the fullerene polymer film is insufficient, this information can be fed back to the polymerization process to control the polymerization conditions of fullerene.

  As long as the heterojunction structure of the present invention has the basic configuration described above, the laminated structure can have various changes, and each layer can be divided into a plurality of layers according to the purpose of use. The layer thickness can be arbitrarily designed.

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Transparent electrode, 3 ... Conductive polymer film, 4 ... Fullerene polymer film,
5 ... Counter electrode, 6 ... Active layer

Patent No. 9656473 Patent No. 95230248 Patent No. 9325116 USP No. 5171373 WO 940505045

Claims (10)

A charge transfer type heterojunction structure in which a conductive organic film made of a polythiophene film and a fullerene polymer film are laminated between a light transmissive electrode and its counter electrode,
Further, in between the fullerene polymer film and the conductive organic film, in between the Enel Gireberu energy level and the conductive organic film Enel Gireberu viewed from the vacuum level is said fullerene polymer film There is an active layer consisting of a phthalocyanine film ,
Photoelectric conversion element.   The photoelectric conversion element according to claim 1, wherein the fullerene polymer film is in contact with the counter electrode.   The photoelectric conversion element according to claim 1, wherein the light transmissive electrode, the conductive organic film, the active layer, the fullerene polymer film, and the counter electrode are laminated in this order on a substrate.   The photoelectric conversion element according to claim 1, wherein the light transmissive electrode, the fullerene polymer film, the active layer, the conductive organic film, and the counter electrode are stacked in this order on a substrate.   The photoelectric conversion element according to claim 1, wherein a dopant for controlling conductivity is added to the conductive organic film. The photoelectric conversion element according to claim 1, wherein the fullerene polymer film is made of a C ⁶⁰ polymer and / or a C ⁷⁰ polymer.   The photoelectric conversion element according to claim 1, wherein the fullerene polymer film is formed by photopolymerization, electron beam irradiation polymerization, plasma polymerization, microwave polymerization, or electrolytic polymerization of fullerene molecules.   The photoelectric conversion element according to claim 1, wherein the light transmissive electrode and the counter electrode are made of a metal oxide or a metal thin film. The light transmissive electrode is made of a metal oxide obtained by doping tin with indium oxide, or a thin film of gold, silver, platinum, or nickel, and the counter electrode is made of a thin film of the metal oxide or aluminum, magnesium, or indium. The photoelectric conversion element according to claim 8 .   The photoelectric conversion element according to claim 1, which is configured as a photocell.

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