Tamotsu Horiuchi

Bio: Tamotsu Horiuchi is an academic researcher from Ricoh. The author has contributed to research in topics: Layer (electronics) & Electrochromism. The author has an hindex of 15, co-authored 94 publications receiving 2756 citations. Previous affiliations of Tamotsu Horiuchi include Kyushu Institute of Technology & Mitsubishi.

High Efficiency of Dye-Sensitized Solar Cells Based on Metal-Free Indoline Dyes

Abstract: We now report metal-free organic dyes having a new type of indoline structure, which exhibits high efficiencies in dye-sensitized solar cells. The solar energy to current conversion efficiencies with the new indoline dye was 6.51%. Under the same conditions, the N3 dye was 7.89% and the N719 dye was 8.26%. The new indoline dye was optimized for the amount of 4-tert-butyl pyridine in the electrolyte and cholic acid as a coadsorbent. Subsequently, the solar energy to current conversion efficiencies reached 8.00%. This value was the highest obtained efficiency for dye-sensitized solar cells based on metal-free organic dyes without an antireflection layer.

Organic Dye for Highly Efficient Solid-State Dye-Sensitized Solar Cells

Abstract: Dye sensitized solar cells are an interesting low cost alter native to conventional solar cells. Efficiencies over 10 % have been achieved. [1,2] Advantageous is the replacement of the liquid electrolyte in these devices with a solid charge carrier material to avoid any sealing and long term stability prob lems. In 1998 Bach et al. [3] demonstrated that the electrolyte can be replaced by a hole conductor. Here we report a very efficient solid state solar cell with the amorphous organic hole transport material 2,2¢,7,7¢ tetrakis (N,N di p methoxyphenyl amine)9,9¢ spirobifluorene (spiro OMeTAD) as hole conduc tor and for the first time an organic metal free indoline dye as sensitizer. Record efficiencies for this type of cell of over 4 % over the solar spectrum were reached. Until now, sensitization using organic dyes has not been as efficient as using ruthenium dyes, which have been success fully applied previously. Metal free dyes such as perylene de rivatives, [4] coumarin dyes, [5] porphyrin dyes, [6] and cyanine and merocyanine dyes [7] have been used as sensitizers, but did not achieve the same solar conversion efficiency as ruthenium dyes. The efficiencies achieved in this work with the indoline dye (D102) are even higher than the highest currently report ed values for ruthenium dye sensitized solid state cells. In ad dition, this dye has the advantage that it can be produced at low cost, because it does not contain the expensive rare metal ruthenium and it is easy to synthesize. Up to now the best results reported with spiro OMeTAD as a hole conductor are efficiencies of 3.2 %. [8] In that work the dye uptake and open circuit voltage were optimized by a sil ver complexation. In the case of the indoline dye we were able to reach an efficiency of just over 4 % without further optimi zation. This shows the extremely high potential of the indoline dye as a sensitizer in solid state dye sensitized solar cells. In doline dyes have previously been used in dye sensitized solar cells with a liquid electrolyte. [9,10] There also they showed a good performance of up to g = 6.1 % conversion efficiency compared to 6.3 % for a N3 dye sensitized cell. [9] Solid state devices usually have a lower performance, which is not the case here with an extraordinary efficiency of 4 %, which ap proaches that of their liquid …

Highly efficient metal-free organic dyes for dye-sensitized solar cells

Abstract: A solar-to-electric conversion efficiency of 5.1% is achieved with this new dye, compared to 5.8% for N3 dye under the same experimental conditions. Although these indoline dyes are slightly less efficient than N3 dye [cis-Ru(II)(2,2′-bipyridil-4,4′-dicarboxilic acid) (NCS)], the cost would be expected much lower because it does not contain any noble, rare metals in the structure and also it is easy to prepare specially for the mass production. Furthermore, indoline dyes are shown to be highly stable to photoredox processes by cyclic voltammogram.

Photoelectric conversion element

Abstract: To provide a photoelectric conversion element, including a first substrate, a first transparent electrode disposed on the first substrate, a hole-blocking layer disposed on the first transparent electrode, an electron-transporting layer that is disposed on the hole-blocking layer and includes an electron-transporting semiconductor on a surface of which a photosensitizing compound is adsorbed, a hole-transporting layer that is connected to the electron-transporting layer and includes a hole-transporting material, and a second electrode disposed on the hole-transporting layer, wherein the photoelectric conversion element includes an output extraction terminal part configured to extract electricity out from the photoelectric conversion element, and the output extraction terminal part is formed with a plurality of micropores piercing through the hole-blocking layer

Dye-Sensitized Solar Cells

Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

Design Rules for Donors in Bulk‐Heterojunction Solar Cells—Towards 10 % Energy‐Conversion Efficiency

Abstract: There has been an intensive search for cost-effective photovoltaics since the development of the first solar cells in the 1950s. [1–3] Among all alternative technologies to silicon-based pn-junction solar cells, organic solar cells could lead the most significant cost reduction. [4] The field of organic photovoltaics (OPVs) comprises organic/inorganic nanostructures like dyesensitized solar cells, multilayers of small organic molecules, and phase-separated mixtures of organic materials (the bulkheterojunction solar cell). A review of several OPV technologies has been presented recently. [5] Light absorption in organic solar cells leads to the generation of excited, bound electron– hole pairs (often called excitons). To achieve substantial energy-conversion efficiencies, these excited electron–hole pairs need to be dissociated into free charge carriers with a high yield. Excitons can be dissociated at interfaces of materials with different electron affinities or by electric fields, or the dissociation can be trap or impurity assisted. Blending conjugated polymers with high-electron-affinity molecules like C60 (as in the bulk-heterojunction solar cell) has proven to be an efficient way for rapid exciton dissociation. Conjugated polymer–C60 interpenetrating networks exhibit ultrafast charge transfer (∼40 fs). [6,7] As there is no competing decay process of the optically excited electron–hole pair located on the polymer in this time regime, an optimized mixture with C60 converts absorbed photons to electrons with an efficiency close to 100%. [8] The associated bicontinuous interpenetrating network enables efficient collection of the separated charges at the electrodes. The bulk-heterojunction solar cell has attracted a lot of attention because of its potential to be a true low-cost photovoltaic technology. A simple coating or printing process would enable roll-to-roll manufacturing of flexible, low-weight PV modules, which should permit cost-efficient production and the development of products for new markets, e.g., in the field of portable electronics. One major obstacle for the commercialization of bulk-heterojunction solar cells is the relatively small device efficiencies that have been demonstrated up to now. [5] The best energy-conversion efficiencies published for small-area devices approach 5%. [9–11] A detailed analysis of state-of-the-art bulk-heterojunction solar cells [8] reveals that the efficiency is limited by the low opencircuit voltage (Voc) delivered by these devices under illumination. Typically, organic semiconductors with a bandgap of about 2 eV are applied as photoactive materials, but the observed open-circuit voltages are only in the range of 0.5–1 V. There has long been a controversy about the origin of the Voc in conjugated polymer–fullerene solar cells. Following the classical thin-film solar-cell concept, the metal–insulator–metal (MIM) model was applied to bulk-heterojunction devices. In the MIM picture, Voc is simply equal to the work-function difference of the two metal electrodes. The model had to be modified after the observation of the strong influence of the reduction potential of the fullerene on the open-circuit volt

Solar energy conversion by dye-sensitized photovoltaic cells

Abstract: The quality of human life depends to a large degree on the availability of energy. This is threatened unless renewable energy resources can be developed in the near future. Chemistry is expected to make important contributions to identify environmentally friendly solutions of the energy problem. One attractive strategy discussed in this Forum Article is the development of solar cells that are based on the sensitization of mesoscopic oxide films by dyes or quantum dots. These systems have already reached conversion efficiencies exceeding 11%. The underlying fundamental processes of light harvesting by the sensitizer, heterogeneous electron transfer from the electronically excited chromophore into the conduction band of the semiconductor oxide, and percolative migration of the injected electrons through the mesoporous film to the collector electrode will be described below in detail. A number of research topics will also be discussed, and the examples for the first outdoor application of such solar cells wi...

Metal-Free Organic Dyes for Dye-Sensitized Solar Cells: From Structure: Property Relationships to Design Rules

Abstract: Dye-sensitized solar cells (DSSC) have attracted considerable attention in recent years as they offer the possibility of low-cost conversion of photovoltaic energy This Review focuses on recent advances in molecular design and technological aspects of metal-free organic dyes for applications in dye-sensitized solar cells Special attention has been paid to the design principles of these dyes and on the effect of various electrolyte systems Cosensitization, an emerging technique to extend the absorption range, is also discussed as a way to improve the performance of the device In addition, we report on inverted dyes for photocathodes, which constitutes a relatively new approach for the production of tandem cells Special consideration has been paid to the correlation between the molecular structure and physical properties to their performance in DSSCs

Organometal Perovskite Light Absorbers Toward a 20% Efficiency Low-Cost Solid-State Mesoscopic Solar Cell

Abstract: Recently, perovskite CH3NH3PbI3 sensitizer has attracted great attention due to its superb light-harvesting characteristics. Organometallic or organic materials were mostly used as sensitizers for solid-state dye-sensitized solar cells at early stages. Inorganic nanocrystals have lately received attention as light harvesters due to their high light-absorbing properties. Metal chalcogenides have been investigated with solid-state dye-sensitized solar cells; however, the best power conversion efficiency was reported to be around 6%. CH3NH3PbX3 (X = Cl, Br, or I) perovskite sensitizer made a breakthrough in solid-state mescoscopic solar cells, where the first record efficiency of around 10% was reported in 2012 using submicrometer-thick TiO2 film sensitized with CH3NH3PbI3. A rapid increase in efficiency approaching 14% followed shortly. In this Perspective, recent progress in perovskite-sensitized solid-state mesoscopic solar cells is reviewed. On the basis of the recent achievements, a power conversion eff...