Hybrid Organic-inorganic Solar Cells Research Articles

Colloidal quantum dot solar cells

Abstract In recent years colloidal quantum dots solar cells have been the subject of extensive research. A promising alternative to existing silicon solar cells, quantum dot solar cells are among the candidates for next generation photovoltaic devices. Colloidal quantum dots are attractive in photovoltaics research due to their solution processability which is useful for their integration into various solar cells. Here, we review the recent progresses in various quantum dot solar cells which are prepared from colloidal quantum dots. We discuss the preparation methods, working concepts, advantages and disadvantages of different device architectures. Major topics discussed in this review include integration of colloidal quantum dots in: Schottky solar cells, depleted heterojunction solar cells, extremely thin absorber solar cells, hybrid organic–inorganic solar cells, bulk heterojunction solar cells and quantum dot sensitized solar cells. The review is organized according to the working principle and the architecture of photovoltaic devices.

Organic-inorganic hybrid solar cells made from hyperbranched phthalocyanines

Organic-inorganic hybrid solar cells with a cell structure of indium tin oxide/TiO2/TiOx:hyperbranched phthalocyanine/CuSCN/Au (or carbon) have been fabricated by solution based processing using three hyperbranched phthalocyanines (H2PPc, TiOPPc and CuPPc) as light-absorbing materials. These organic-inorganic hybrid solar cells are extremely thin absorber solar cells, which possess p-i-n heterojunctions ("i," an intrinsic absorber layer), as they were confirmed by scanning electron microscopy. With an illuminated area of 1 cm2, a solar cell made from H2PPc achieved conversion efficiency of 0.23% under 1-sun air mass 1.5 global illumination. The lower conversion efficiency for the cell made from CuPPc was likely due to the energy loss in the formation of triplet states with an intersystem crossing time of 0.76 ps.

Large-Area Silicon Nanowires from Silicon Monoxide for Solar Cell Applications

Large-area upstanding silicon nanowires (SiNWs) were synthesized by hot-filament chemical vapor deposition (HFCVD) using silicon monoxide (SiO) powder as Si source under high vacuum (1.2 x 10(-5) Torr). Gold nanoparticles (AuNPs) were employed as catalyst, which were formed on Si substrate by in-situ reduction of gold chloride (AuCl3). The size and distribution of the Au nanoparticles can be easily controlled through chemical reaction conditions. Consequently, the diameter, length and density of SiNWs could be varied in certain range. The SiNWs obtained are single crystalline with growth directions predominantly along [01-1]. Silicon nanowires in large-scale and diameter less than 10 nm can be grown on different Si substrates with this method. Organic inorganic hybrid solar cells based on SiNWs arrays have been demonstrated.

Broad Spectrum Light Harvesting in TiO$_2$ Nanotube Array – Hemicyanine Dye – P3HT Hybrid Solid-State Solar Cells

Control of interfacial electron transfer between electron transporting oxide semiconductors and molecular adsorbates in organic-inorganic hybrid solar cells is a research area of intense interest, with the poor optical harvesting in the red and near-IR (NIR) portion of the solar spectrum a significant limitation to device performance. We fabricate hybrid solar cells, using two new hemicyanine photosensitizers having different π-conjugation lengths that absorb sunlight from visible to NIR range, as well as unsymmetrical squaraine dye. These organic dyes are used not only as a photosensitizer, but also as electronic mediator for n-type TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanotube arrays, vertically oriented from the fluorine-doped tin oxide coated glass substrate, which are subsequently infiltrated with p-type regio-regular poly(3-hexyl thiophene 2,5 diyl), enabling broad-spectrum response. In general, the organic-dye-inorganic photovoltaic structure appears a promising method for harvesting a broad portion of the solar spectrum energy from a relatively simple photovoltaic device.

Effects of Insulation Coating with Metal Salt on the Performance of Organic-Inorganic Hybrid Solar Cells

This work reports on the preparation of modified TiO2 electrodes, which could be applied to the photoanodes in a dye-sensitized solar cells (DSSCs). TiO2 layer was formed on a FTO (fluorine-doped tin oxide) coated glass via doctor-blade method and post heat treatment. Then, the various metal hydroxides and metal oxides were selectively deposited onto the TiO2 layers via electrophoretic deposition and annealing process to give modified TiO2 layer in DSSCs. When metal hydroxide-deposited electrodes were employed in DSSCs, photovoltaic efficiencies were improved by ca. 3–16% compared to those of the cells with bare TiO2 electrodes. However, it was found that the efficiencies regressed when the metal hydroxides were converted to metal oxides via the annealing process.

Impact of energy alignment and morphology on the efficiency in inorganic–organic hybrid solar cells

Carrier transport in hybrid inorganic–organic solar cells has been studied by means of a two-dimensional drift-diffusion-based model including the generation and motion of excitons. The devices consist of a polymer serving as donor material and a semiconducting small-band gap inorganic component as acceptor material. For the first time it is taken into account that, in strong contrast to purely organic or inorganic cells, charge carriers can be generated at the heterojunction (due to dissociation of the donor excitons) and in the bulk of the acceptor material (due to band to band generation in the inorganic material). The efficiencies of devices were investigated dependent on (i) the donor–acceptor interface geometry, (ii) the transport level offsets at the heterojunction, and (iii) the energy barriers formed at the contacts. For each case, a detailed analysis of the behavior is given. We demonstrate that, depending on the particular scenario, each of these three factors can be responsible for profoundly reduced efficiencies and pronounced s-shaped sections in the I– V curves. Moreover, we show that each of the investigated factors may give rise to equally serious efficiency losses. However, it is not possible to identify a dominant effect. Depending on the particular combination, the efficiency can vary by two orders of magnitudes. In order to avoid such losses, our theoretical assessment reveals that suitable material combinations are required to form (i) ohmic contacts, (ii) preclude formation of isolated islands or nanoparticles during growth, and (iii) possess a hole-blocking offset in the transport levels at the heterojunction.

Electrochemical Deposition of ZnO Nanorods on Transparent Reduced Graphene Oxide Electrodes for Hybrid Solar Cells

Monocrystalline ZnO nanorods (NRs) with high donor concentration are electrochemically deposited on highly conductive reduced graphene oxide (rGO) films on quartz. The film thickness, optical transmittance, sheet resistance, and roughness of rGO films are systematically studied. The obtained ZnO NRs on rGO films are characterized by X-ray diffraction, transmission electron microscopy, photoluminescence, and Raman spectra. As a proof-of-concept application, the obtained ZnO NRs on rGO are used to fabricate inorganic-organic hybrid solar cells with layered structure of quartz/rGO/ZnO NR/poly(3-hexylthiophene)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (P3HT/PEDOT:PSS)/Au. The observed power conversion efficiency (PCE, eta), approximately 0.31%, is higher than that reported in previous solar cells by using graphene films as electrodes. These results clearly demonstrate that rGO films with a higher conductivity have a smaller work function and show a better performance in the fabricated solar cells.

Hybrid solar cells based on poly(3-hexylthiophene) and electrospun TiO2 nanofibers with effective interface modification

Electrospinning, a low cost production method for large area nanofibrous films, is employed to fabricate organic-inorganic hybrid solar cells based on poly(3-hexylthiophene) and TiO2 nanofibers. The performance of the hybrid solar cells is optimized by modifying the surface of TiO2 nanofibers with ruthenium dye (N719) and 3-phenylpropionic acid, which results in the average power conversion efficiency of about 1.1% under AM 1.5G simulated illumination (100 mW cm−2). It is found that the co-modification of N719 and 3-phenylpropionic acid on TiO2 can induce more ordered backbone packing of poly(3-hexylthiophene) layer, lower density of trap states on the surface of TiO2 and longer lifetime of carriers in the active layer due to retarded recombination process by the modifier. Therefore the interface modification can dramatically enhance the photovoltaic performance.

Electropolymerized poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) film on ITO glass and its application in photovoltaic device

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films have been electrochemically polymerized in situ on ITO glass substrate in boron trifluoride diethyl etherate electrolyte (BFEE). Cyclic voltammograms show good redox activity and stability of the PEDOT films. These films had been directly used to fabricate organic–inorganic hybrid solar cells with the structure of ITO/PEDOT/ZnO:MDMO-PPV/Al. The solar cells made of electrochemically polymerized films exhibit higher energy conversion efficiencies compared with that prepared by the spin-coating method, and the highest value is 0.33%. This in-situ electropolymerized method effectively simplifies fabricating procedures and may blaze a facile and economical route for producing high-efficiency solar cells.

Sponge-like structures for application in photovoltaics

Large surface areas at an interface between two different materials are desired in many research fields where the interaction between these materials significantly affects the performance of the physical system. This behaviour is illustrated on sponge-like structures, which assign for such a high surface area, and demonstrate the development from bulk material to thin films and a variety of applications. The focus is on sponge-like nanostructures consisting of a network of aggregated titania nanoparticles applied in hybrid structures for photovoltaics. Examples based on a sol-gel process for the preparation of titania nanostructures in thin films, mimicking the sponge morphology, are shown. In general, titania films are widely used in photovoltaics, contributing to a large surface area available for interfacial reactions, e.g. charge carrier transfer routes. Interpenetrating networks with dimensions matching exciton diffusion lengths in the polymer component of a hybrid organic-inorganic photovoltaic structure are highly desirable. To characterize the fabricated morphology, atomic force microscopy and field-emission scanning electron microscopy are employed in real space. The advanced scattering technique of grazing-incidence small-angle X-ray scattering complements the characterization in reciprocal space. From the obtained results, the sponge-like morphology is verified, a physical description of the morphology with statistical relevance is constructed and the successful complete filling of the network is shown. According to this description, the presented sponge-like titania nanostructures are well suited for use in hybrid organic-inorganic solar cells.

Fabrication and characterization of inorganic-organic hybrid solar cells based on CuInS2

Chalcopyrite compounds/fullerene solar cells based on copper-indium-disulphide and C60 were produced. Two-types of devices with heterojunction and bulk heterojunction structures were examined and characterized. The bulk heterojunction structure provided better efficiency compared to that of the heterojunction structure. Nanostructures of the solar cells were confirmed as mixed nanocrystals by transmission electron microscopy. A photovoltaic mechanism of the present solar cells was discussed on the basis of the experimental results.

Efficient electron transfers in ZnO nanorod arrays with N719 dye for hybrid solar cells

Hybrid organic–inorganic solar cells have been focused on producing materials in the combination of metal oxide with high electron mobility and organic semiconductors of conjugated polymers. In this article, we demonstrated the charge injection efficiency of hybrid solar cell consisting of poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C 61 butyric acid methyl ester (PCBM)/ZnO with and without N719 dye molecule. After the modification of ZnO nanorod arrays with N719, short-circuit current density ( J sc) of 8.89 mA/cm 2 was obtained, and it was 1.5 times higher than that of without the N719. The power conversion efficiency was enhanced from 1.16% to 2.0% through the additional surface modification of the ZnO nanorod array with N719 dye.

Organic photovoltaic cells made from sandwich-type rare earth phthalocyaninato double and triple deckers

This work presents organic-inorganic hybrid solar cells, which possess the capability for broad band photon harvesting from an ultraviolet-visible to a near infrared range. These solar cells are bulk heterojunction devices, which have been fabricated by free base phthalocyanine and rare earth phthalocyaninato double or triple deckers (electron donors) with a perylenediimide derivative (electron acceptor). Two-type cell structures with or without nanostructured TiO2 layers have been presented. A characterization of the structures, steady state spectroscopy, fluorescence dynamics, and photoelectrical property of these cells and the active materials has been carried out. A cell structure of In2O3:SnO2∕TiO2-active material-TiO2∕Al has shown a significant improvement in conversion efficiency.

반도체형 고분자를 이용한 태양전지섬유

Organic semi-conductive materials have characteristics such as the advantages of easy formability, low-cost and diversity along with moderate semi-conductive properties. In this paper, we developed a flexible organic-inorganic hybrid solar cell fiber. First, we made a solar cell on the glass and attached the solar cell on the glass fiber similarly. In the latter case, thermal deposition method was employed in order to effectively apply ITO onto fiber surface. The amount of ITO was controlled by varying the temperature from 25, 150 to . Optimum result was obtained at where maximize the deposition amount without significant decomposition of ITO. Despite of maximum open circuit voltage of 0.39V, the resulting current was quite unstable and weak, limiting realistic applications. It was, however, concluded that the flexible solar cell fiber developed showed a possibility of low-weight application from functional clothing for military to space suit mainly due to flexibility and thus wear ability.

TiO2 Nanotube Arrays by using ZnO Nanorod Template through Liquid Phase Deposition for Organic- Inorganic Hybrid Photovoltaic Cells

ABSTRACTTiO2 nanotube arrays had been selected as electron transport material incorporate with P3HT:PCBM blended polymer to fabricate the hybrid organic-inorganic solar cells. Well aligned TiO2 nanotube arrays has been synthesized though the liquid phase deposition by using ZnO nanorod arrays as templates. Three types of dyes (viz. NKX-2677, D149, N719) were adsorbed onto the surface of TiO2 nanotube arrays to increase the interfacial contacts between the organic polymer and inorganic metal oxide. Surface modification with NKX-2677 exhibited remarkable improvement of the cell efficiencies in terms of current density, open circuit voltage, and fill factor as compared with those of other dyes.

Semiconductor Oxides as Electron Acceptors in Hybrid Organic-Inorganic Solar Cells

Hybrid Solar Cells (HSCs) were prepared as bi-layers between thin film semiconductor oxides (TiO2, Nb2O5 and ZnO) made by the sol-gel solution and the polymer MEH-PPV, applying a final device configuration ITO/Oxidethin film/MEH-PPV/Ag. We have analyzed the photovoltaic response in terms of inert atmosphere by recording the initial values of open circuit voltage (Voc) and current density (Jsc) and also by analyzing the corresponding IV-curves. We report in this work the improvement observed in Jsc, Voc and IV-curves when HSCs are transferred from inert conditions to ambient atmosphere. The effect is observed regardless of the semiconductor oxide applied and has been attributed to the reversible incorporation of oxygen from the atmosphere into the semiconductor oxide surface during illumination.

Organic–inorganic hybrid solar cells based on conducting polymer and SnO 2 nanoparticles chemically modified with a fullerene derivative

Organic–inorganic hybrid solid solar cells were fabricated by using a conjugated polymer (MDMO-PPV) and SnO 2 nanoparticles chemically modified with C 60C(COOH) 2. The cell performance was improved by the chemical modification, suggesting that the modification with photoelectrochemically active organic materials is useful for establishing good electronic junction at the organic–inorganic interface. The short-circuit current density J SC increased with increasing thickness of MDMO-PPV up to 40 nm, and then decreased gradually. This thickness dependence was explained by the fluorescence quenching of MDMO-PPV by Au electrode and the film resistance of MDMO-PPV.

Fabrication and characterization of 4-tricyanovinyl- N, N-diethylaniline/p-silicon hybrid organic–inorganic solar cells

Hybrid organic–inorganic solar cell was fabricated by thin film of 4-tricyanovinyl- N, N-diethylaniline deposited on p-Si substrates. The capacitance–voltage characteristics indicated that the junction is of abrupt nature. The dark forward current density-voltage characteristics indicated a tunneling conduction at relatively low voltages followed by a space-charge-limited-conduction mechanism at relatively high voltages. Under illumination, the cell exhibits photovoltaic characteristics with an open-circuit voltage of 0.70 V, a short-circuit current density of 9.15 mA cm −2, and a power conversion efficiency of 3.10%. The effect of γ-rays irradiation (100 kGy absorbed dose) on the characteristics of the cell was also investigated. The fill factor and the power conversion efficiency decrease by 20.9% and 39% of the original value, respectively.

Improvement of charge injection efficiency in organic-inorganic hybrid solar cells by chemical modification of metal oxides with organic molecules

The effect of chemical modification of metal oxide surface with dye molecules in organic-inorganic hybrid solid solar cells was studied by using double layered cells consisting of poly(3-hexylthiophene) (P3HT) and a flat layer of dense TiO2. The external quantum efficiency of the chemically modified cell was nearly double that expected from the photosensitizing effect of the dye molecules. The additional increase shows that the chemical modification with dye molecules can serve not only as a photosensitizer but mainly as an energy funnel and/or an electronic mediator to significantly improve the electron injection efficiency from P3HT to TiO2.

Hybrid Solar Cells with Prescribed Nanoscale Morphologies Based on Hyperbranched Semiconductor Nanocrystals

In recent years, the search to develop large-area solar cells at low cost has led to research on photovoltaic (PV) systems based on nanocomposites containing conjugated polymers. These composite films can be synthesized and processed at lower costs and with greater versatility than the solid state inorganic semiconductors that comprise today's solar cells. However, the best nanocomposite solar cells are based on a complex architecture, consisting of a fine blend of interpenetrating and percolating donor and acceptor materials. Cell performance is strongly dependent on blend morphology, and solution-based fabrication techniques often result in uncontrolled and irreproducible blends, whose composite morphologies are difficult to characterize accurately. Here we incorporate three-dimensional hyperbranched colloidal semiconductor nanocrystals in solution-processed hybrid organic-inorganic solar cells, yielding reproducible and controlled nanoscale morphology.