Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• • H—ELECTRICITY
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  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/10—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising heterojunctions between organic semiconductors and inorganic semiconductors
  • H10K30/15—Sensitised wide-bandgap semiconductor devices, e.g. dye-sensitised TiO2
  • H10K30/151—Sensitised wide-bandgap semiconductor devices, e.g. dye-sensitised TiO2 the wide bandgap semiconductor comprising titanium oxide, e.g. TiO2
• • H—ELECTRICITY
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  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/30—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/80—Constructional details
  • H10K30/81—Electrodes
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  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
  • H10K2102/10—Transparent electrodes, e.g. using graphene
  • H10K2102/101—Transparent electrodes, e.g. using graphene comprising transparent conductive oxides [TCO]
  • H10K2102/103—Transparent electrodes, e.g. using graphene comprising transparent conductive oxides [TCO] comprising indium oxides, e.g. ITO
• • H—ELECTRICITY
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  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/50—Photovoltaic [PV] devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/10—Organic polymers or oligomers
  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
  • H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/10—Organic polymers or oligomers
  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
  • H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
  • H10K85/1135—Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/20—Carbon compounds, e.g. carbon nanotubes or fullerenes
  • H10K85/211—Fullerenes, e.g. C60
  • H10K85/215—Fullerenes, e.g. C60 comprising substituents, e.g. PCBM
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/549—Organic PV cells

Definitions

• This invention relates to improved architecture for polymer-based photovoltaic cells and methods for the production of cells having the improved architecture.
• Photovoltaic cells having active layers based on organic polymers, in particular polymer-fullerene composites are of interest as potential sources of renewable electrical energy.
• Such cells offer the advantages implied for polymer-based electronics, including low cost fabrication in large sizes and low weight on flexible substrates. This technology enables efficient "plastic" solar cells which would have major positive impacts on the world's energy needs.
• Polymer-based photovoltaic cells may be described as thin film devices fabricated in the metal-insulator-metal (MIM) configuration sketched in Fig. IA.
• MIM metal-insulator-metal
• Fig. IAl Devices of the art have had the configuration shown in Fig. IAl as device 10.
• an absorbing and charge-separating bulk heterojunction layer 11, (or "active layer") with thickness of approximately 100 ran is sandwiched between two charge-selective electrodes 12 and 14.
• These electrodes differ from one another in work function.
• the work function difference between the two electrodes provides a built-in potential that breaks the symmetry thereby providing a driving force for the photo-generated electrons and holes toward their respective electrodes with the higher work function electrode 12 collecting holes and the lower work function electrode 14 collecting electrons.
• these devices of the art also include a substrate 15 upon which the MIM structure is constructed. Alternatively, the positions of the two electrodes relative to the support can be reversed. In the most common configurations of such devices, the substrate 15 and the electrode 12 are transparent and the electrode 14 is opaque and reflective such that the light which gives rise to the photoelectric effect enters the device through support 15 and electrode 12 and reflects back through the device off of electrode 14.
• the prerequisites for an ideal optical spacer layer 19 include the following: First, the layer 19 should be constructed of a material which is a good acceptor and an electron transport material with a conduction band edge lower in energy than that of the highest occupied molecular orbital (HOMO) of the material making up the active layer; Second, the layer 19 should be constructed of a material having the energy of its conduction band edge above (or close to) the Fermi energy of the adjacent electron-collecting electrode: and Third, it should be transparent over a significant portion of the solar spectrum.
• HOMO highest occupied molecular orbital
• the layer 19 should be of a thickness which, taking into consideration the material from which the layer is formed and that material's index of refraction, provides a redistribution of a significant portion of the internal reflection within the device. As shown in Fig. 1 A4 this configuration can reduce or eliminate the dead zone 16 in active layer 11.
• this invention in one embodiment, provides an improved photovoltaic cell.
• This cell includes an organic polymer active layer having two sides. One side is bounded by a transparent first electrode through which light can be admitted to the active layer. The second side is adjacent to a light-reflective second electrode which is separated from the second side by an optical spacer layer.
• the spacer layer is substantially transparent in the visible wavelengths. It
• SVCA 31688.1 increases the efficiency of the device by modifying the spatial distribution of the light intensity within the photoactive layer, thereby creating more photogenerated charge carriers in the active layer.
• the spacer layer is constructed of a material that is a good acceptor and an electron transport material with a conduction band lower in energy than that of the highest occupied molecular orbital of the organic polymer making up the photoactive layer.
• the spacer layer is further characterized as being constructed of a material having the energy of its conduction band edge above or close to the Fermi energy of the adjacent electron-collecting electrode.
• the spacer layer has an optical thickness equal to about a quarter of the wavelength of at least a portion of the incident light.
• optical thickness refers to the actual physical thickness of the layer multiplied by the index of refraction of the material from which the layer is formed.
• the spacer layer is constructed of a metal oxide, in particular a substantially amorphous metal oxide and especially substantially amorphous titanium oxide or zinc oxide.
• titanium oxide is used to describe a material of construction for the layer 19 it is intended to refer not only to amorphous titanium dioxide but also, and generally preferably, to titanium suboxide.
• TiO x titanium oxide in which the titanium is less than completely oxidized and which is referred to herein as TiO x with the understanding that "x" in this formula is generally less than 2, for example from about 0.7 to just less than 2.
• metal oxide materials While preferred, are merely representative.
• Other materials meeting the optical and electrical selection criteria just recited may be used as well. These other materials can include conductive organic polymers meeting the criteria set out above.
• Other representative inorganic materials include amorphous silicon oxide; SiO x , where x is the same as x in TiO x oxide, and indium-zinc and lithium-zinc mixed oxides (InZn oxide and LiZn oxide) for example.
• the hole-collecting electrode is a bilayer electrode and the active layer comprises an organic polymer in admixture with a fullerene.
• this invention provides an improved method of preparing an organic polymer-based photovoltaic cell comprising a transparent substrate, a transparent hole-collecting electrode on the support, and an organic polymer-based active layer on the hole-collecting electrode.
• the improvement comprises casting a layer of a titanium oxide precursor solution onto the active layer and thereafter heating the cast layer of titanium oxide precursor to convert the precursor to titanium suboxide to provide a spacer layer.
• Fig. IAl is a schematic cross-sectional view of a photovoltaic cell device of the prior art
• Fig. 1 A2 is a schematic cross-sectional view of a photovoltaic cell device of this invention with its added spacer layer;
• Fig. 1 A3 is a schematic view of a photovoltaic cell device of the prior art presenting the distribution of the squared optical electric field strength (E 2 ) inside a representative device of the prior art which lacks an optical spacer
• E 2 squared optical electric field strength
• Fig. 1 A4 is a schematic view of a photovoltaic cell device of the invention illustrating the distribution of the squared optical electric field strength (E 2 ) inside a representative device of the invention which includes an optical spacer;
• Fig. IBl is a schematic illustration of a representative thin film photovoltaic cell of the present invention in which the device consists of a composite of conjugated
• ITO transparent indium-tin mixed oxide
• PEDOT:PSS poly(styrenesulfonate)
• Fig. 1B2 illustrates the energy levels of the single components of the representative photovoltaic cell shown in Fig. IBl, which show that this device exhibits excellent band matching for cascading charge transfer;
• Fig. 2 A is a tapping mode atomic force microscope image which shows the surface morphology of a representative TiO x spacer film
• Fig. 2B is a graph showing X-ray diffraction patterns of a representative relatively amorphous TiO x spacer layer formed at room temperature (bottom curve) and OfTiO 2 powder that has been calcined at 50O 0 C (top curve) and exhibits a much more pronounced crystalline structure;
• Fig. 2C is the absorption spectrum of a spin coated TiO x film which can serve as a representative spacer layer in the photovoltaic cells of this invention. This spectrum shows that the TiO x film is transparent in the visible range;
• Fig. 3 A is a graph in which the incident monochromatic photon to current collection efficiency (IPCE)] spectra are compared for the two representative devices with and without a TiO x optical spacer layer;
• IPCE current collection efficiency
• Fig. 3B is a pair of absorption spectra obtained from reflectance measurements in which the lower curve depicts the absolute value of the absorbance of the P3HT:PCBM active layer composite and the upper curve depicts the ratio of the intensity of reflectance observed with devices of this invention with their spacer layers divided by the intensity of reflection under the same conditions in devices of the prior art which do not include the spacer layer.
• the inset is a schematic description of the optical beam path in the samples used to determine the upper curve in Fig. 3B; and
• SVGA 31688.1 Fig. 4A is a pair of graphs showing the current density- voltage characteristics of representative polymer photovoltaic cells with and without a representative TiO x optical spacer illuminated with 25 mW/cm2 at 532 nm.
• Fig. 4B is a pair of graphs showing the current density- voltage characteristics of representative polymer photovoltaic cells with and without a representative TiO x optical spacer illuminated under AMI .5 conditions with a calibrated solar simulator with radiation intensity of 90 mW/cm2.
• Fig. 5. is a series of graphs showing the current density- voltage characteristics of representative polymer photovoltaic cells with and without representative zinc oxide optical spacers illuminated with 25 mW/cm 2 at 532 nm.
• the present photovoltaic cells to which the spacer is added include the following elements: a substrate/support; a hole-collecting electrode; an active layer; and an electron-collecting electrode. These elements will be described and then
• the substrate provides physical support for the photovoltaic device. In most configurations, light enters the cell through the substrate such that the substrate is transparent.
• a material is "transparent" when it provides at least 70% and preferably at least 80% average transmission over the visible wavelengths of about 400 nm to about 750 nm, and preferably significant transmission in the infrared and ultraviolet regions of the solar spectrum, as well.
• suitable transparent substrates include rigid solid materials such as glass or quartz and rigid and flexible plastic materials such as polycarbonates and polyesters for example poly(ethylene terphthalate) (“PET").
• rigid solid materials such as glass or quartz
• rigid and flexible plastic materials such as polycarbonates and polyesters for example poly(ethylene terphthalate) (“PET").
• This electrode is very commonly on or adjacent to the substrate and is in the transmission path of light into the cell. Thus, it should be “transparent” as defined herein, as well.
• This electrode is a high work function electrode.
• the high work function electrode is typically a transparent conductive metal- metal oxide or sulfide material such as indium-tin oxide ("ITO") with resistivity of 20 ohm/square or less and transmission of 89% or greater @ 550 nm. Other materials are available such as thin, transparent layers of gold or silver.
• a "high work function" in this context is generally considered to be a work function of about 4.5eV or greater.
• This electrode is commonly deposited on the solid support by thermal vapor deposition, electron beam evaporation, RF (radio frequency) or Magnetron sputtering, chemical deposition or the like. These same processes can be used to deposit the low work-function electrode as well.
• the principal requirement of the high work function electrode is the combination of a suitable work function, low resistivity and high transparency.
• the hole-collecting electrode is accompanied by a hole-transport layer located between the high work function electrode and the active layer. This provides a "bilayer electrode”.
• SVCA 31688.1 When a hole-transport layer is present to provide a bilayer electrode, it is typically 20 to 30 am thick and is cast from solution onto the electrode.
• materials used in the transport layer include semiconducting organic polymers such as PEDOT:PSS cast from a polar (aqueous) solution or the precursor of poly(bis tetraphenyldiamino ⁇ iphenyl-perfluorocylcobutane) (" ⁇ oly(BTPD-Si-PFCB)" [S. Liu, X. Z. Jiang, H. Ma, M. S. Liu, A. K.-Y. jen, Macro., 2000, 33, 3514; X. Gong, D. Moses, A. J.
• PEDOT.-PSS is preferred.
• PLEDs polymer-based light-emitting diodes
• the Active Layer is the Active Layer
• the active layer is made of two components — a conjugated polymer which serves as an electron donor and a second component which serves as an electron acceptor.
• the second component can be a second conjugated organic polymer but better results are achieved if a fullerene is used.
• organic active layer defined as "a polymer” or as “conjugated” can also contain small organic molecules as described by P. Peumans, S. Uchida and S.R. Forrest, NATURE, 2003, 425, 158. (Incorporated by reference.)
• Conjugated polymers include polyphenylenes, polyvinylenes, polyanilines, polythiophenes and the like. We have had our best results with poly(3- hexylthiophene), (“P3HT”), as conjugated polymer.
• P3HT poly(3- hexylthiophene),
• fullerenes particularly buckminsterfullerene ("C 60 "), as electron acceptors (U.S. Pat. No. 5,454,880), the charge carrier recombination otherwise typical in the photoactive layer may be largely avoided, which leads to a significant increase in efficiency.
• This electrode is a reflective low work function electrode, most commonly a metal and particularly an aluminum electrode. This electrode can be laid down using vapor deposition methods.
• the spacer layer is made from organic or inorganic materials meeting the electrical and optical criterion set forth in the Statement of the Invention above.
• TiO x titanium oxide
• SiO x and zinc oxide give good results.
• Titanium dioxide might be considered a promising candidate as an electron acceptor and transport material as confirmed by its use in dye-sensitized Grazel cells (12,13), hybrid polymer/TiO 2 cells (14-16), and multilayer Cu- phthalocyanine/dye/TiO 2 cells (9,17).
• crystalline TiO 2 is used either in the anatase phase or the rutile phase both of which require treatment at high temperatures (T > 450°C) that are inconsistent with the device architecture shown in Fig. IB.
• the polymeric photoactive layers such as those made of polymer/C 60 composite cannot survive such high temperatures.
• TiO x substantially amorphous titanium oxide
• Fig. IB polymer-fullerene active layer
• Dense TiO x films were prepared using a TiO x precursor solution or suspension, as described in detail elsewhere (18). A layer of the precursor solution/suspension was spin-cast in air on top of the polymer-fullerene composite layer. The sample with its layer of precursor solution/suspension was then heated
• the resulting TiO x films are transparent and smooth with surface features less than a few nm.
• the spacer layer can be from about 8 nm to about 1000 nm in physical thickness, especially from about 20 nm to about 500 nm. Ideally, the layer should present a smooth continuous layer with an "optical thickness" on the general order of 1 A the wavelength of at least a portion of the light being directed onto the cell. As noted previously, "optical thickness" is the product of the physical thickness and the index of refraction. Indices of refraction for the materials from which the spacer layer is prepared run from a high of about 2.75 for some of the inorganic materials down to about 1.32 for the lowest index organic spacer layer materials. Amorphous titanium oxide (TiO x ) has an index of about 2.5-2.6.
• the wavelengths of "light” should be considered to include not only the visible spectrum (about 400 nm to about 750 nm) but also the infrared (about 750 nm to about 2500 nm) and ultraviolet (100 nm to about 400 nm) portions of the solar spectrum. These considerations lead to physical thicknesses for the spacer layer which can range anywhere from about 9 nm for the highest index (2.75) inorganic materials when considering the shortest ultraviolet wavelengths (100 nm wavelength) up to about 500 nm thickness when using the lowest index (1.32) organic materials and considering the longest infrared wavelengths (2500 nm wavelength).
• this range of indexes leads to thickness of from about 35 nm to about 150 nm.
• SVCA 31688.1 range from 35-75% and especially 42.13% - 56.38% that of stoichiometric TiO 2 ; hence TiO x .
• x is less than 2 such that the material is a "suboxide" usually x is from 0.75 to 1.96, preferably 0.8 to 1.9 and especially 0.9 to 1.9. These values also represent from 35% to 98% full oxidation, preferably 40% to 95% and especially 45% to 95% full oxidation.
• solvent processing a layer of a solution or suspension (such as a colloidal suspension) of TiO x or more commonly one or more TiO x precursors is applied.
• the precursor can be converted to TiO x such as by hydrolysis and condensation processes as follows:
• solvent is removed, most commonly by evaporation under mild heating and/or vacuum conditions to yield a continuous thin spacer layer of precursor or TiO x .
• TiO x precursor are based on include solutions of titanium(rV) lower alkoxides such as 1-4 carbon alkoxides including the titanium(IV) butoxides, titanium(IV) propoxides, titanium(IV) ethoxide, and titanium(rV) methoxide.
• Such titanium materials are commonly available and soluble in lower alkanols such as 1-4 carbon alkanols which are liquids that are generally compatible with and nondestructive to other organic polymer layers commonly found in microelectronic devices.
• Alkoxyalkanols such as methoxy-ethanol and the like can be used as well as solvent for these solutions.
• Other titanium sources including titanium salts such as Ti(S O 4 ) 2 and TiCl 4 , and higher alkoxides, and other organometallic compounds and complexes of titanium can be used .
• the solvent selected should dissolve and suspend the TiO x precursor but should not appreciably react with the TiO x precursor. This suggests that care should be used if aqueous solvents or mixed aqueous/organic solvents are used as a substantial concentration of the water component could cause premature reaction such as hydrolysis of the TiO x precursor or more complete reaction of the precursor to TiO x than is preferred.
• the reaction postulated for the formation of TiO x uses water but these are small-stoichiometric scale amounts of water, i.e. for say 2 to 10 moles of water per mole of titanium and not gross quantities as would be present in a mixed solvent. Such small amount of water can enter the reaction zone from ambient conditions, i.e. routine humidity, during the formation of the precursor solution/suspension and for the spin-casting of the layer.
• titanium source/solvent combination Another factor to be considered in selecting a titanium source/solvent combination is the ability of the combination to wet the substrate or underlayer upon which the solution is being spread.
• the lower alkanol-based solutions/suspensions set forth above have given good wetting with the organic polymer substrate layers found in organic polymer-based photovoltaic cells.
• Titanium concentration in the solution/suspension can vary from as low as 0.01 % by weight to as much as 10% by weight or greater. While this has not been optimized, concentrations of from about 0.5 to 5% by weight have given good results.
• TiO x precursor solution/suspension is spread using conventional methods. Spin casting has given good results.
• the precursor solution is formed by heating the solution of starting materials for a time and at a temperature suitable to react the starting material but not so high as to cause conversion of the starting material to a full stiochiometric oxide. Temperatures of from about 50°C to about 150°C and times of from about 0.1 hour (at the higher temperatures) to about 12 hours (at the lower temperatures) can be employed. Preferred temperature and time ranges are from about 80°C to about 120°C for from 1 to 4 hours, again with the higher temperatures using the shorter times and the lower temperatures using the longer times.
• SVGA 31688.1 (PCBM) as the acceptor.
• PCBM PCBM
• the device structure is shown in Fig. IB.
• Fig. 3 A compares the incident photon to current collection efficiency spectrum (IPCE) of devices fabricated with and without the TiO x optical spacer.
• IPCE current collection efficiency spectrum
• the conventional device shows the typical spectral response of the P3HT:PCBM composites with a maximum IPCE of -60% at 500nm, consistent with previous studies (3-6).
• the results demonstrate substantial enhancement in the IPCE efficiency over the entire excitation spectral range; the maximum reaches almost 90% at 500nm, corresponding to a 50% increase in IPCE.
• r out ( ⁇ ) is the intensity of the reflected light from the device with the optical spacer and I out ( ⁇ ) is the intensity of the reflected light from an identical device without the optical spacer.
• the TiO x optical spacer increases the number of carriers per incident photon collected at the electrodes.
• the enhancement in the device efficiency that results from the optical spacer can be directly observed in the current density vs. voltage (J-V) characteristics under monochromatic illumination with 25 mW/cm2 at 532 nm.
• the results demonstrate substantially improved device performance; Jsc increases to 11.80 mA/cm2, the FF increases slightly to 0.45, while Voc remains at 0.62 V.
• Organic spacer layers can be used as well. Such organic spacer materials can be dissolved in water and/or methanol for coating this material on top of the organic layer without damage.
• candidates for organic spacer materials are recently-developed water-soluble ionic polymers such as anionic poly (fluorene) ("anion-PF"), cationic poly (fluorine)("cation-PF”), poly ⁇ [9,9-bis(6'-(N,N,N-tri-methylammonium)-fluorene- 2,7-diyl]- ⁇ /t-[2,5-bis ⁇ 7-phenylene)-l,3,4-oxadiazole] ⁇ ("PFON + (CH 3 ) 3 rPBD”), poly(vinylcarbazole)sulfonate lithium salt (“PVK-SO 3 Li”), t-butyl-2,3,4-oxadiazole sulfonate sodium salt ('V-Bu-PBD-SO 3 Na”), and the like.
• the sol-gel procedure for producing TiO x is as follows; titanium isopropoxide (Ti[OCH(CH 3 ) 2 ] 4 , Aldrich, 97%, 1OmL) was prepared as a precursor, and mixed with 2- methoxyethanol (CH 3 OCH 2 CH 2 OH, Aldrich, 99.9+%, 15OmL) and ethanolamine (H 2 NCH 2 CH 2 OH, Aldrich, 99.5+%, 5mL) in a three-necked flask equipped with a condenser, thermometer, and argon gas inlet/outlet. Then, the mixed solution was heated to 8O 0 C for 2 hours in silicon oil bath under magnetic stirring, followed by heating to 120°C for 1 hour. The two-step heating (8O 0 C and 12O 0 C) was then repeated.
• the typical TiO x precursor solution was prepared in isopropyl alcohol.
• PEDOT:PSS poly(3,4- ethylenedioxylenethiophene)-polystyrene sulfonic acid
• PEDOT:PSS poly(3,4- ethylenedioxylenethiophene)-polystyrene sulfonic acid
• a thin layer of P3HT:PCBM was spin-cast onto the PEDOT:PSS with a thickness of 100 nm.
• the TiO x precursor layer (30 nm) was spin-cast onto the P3HT:PCBM composite from the precursor solution followed by annealing at 9O 0 C for 10 minutes. This casting and heating were carried out under ambient moisture conditions so that the small amounts of water needed to complete the conversion of precursor to TiO x were present.
• the Al electrode was thermally evaporated onto the TiO x layer in vacuum at pressures below 10-6 Torr.
• the sol-gel procedure for producing titanium oxide (TiO x ) is as follows; titanium isopropoxide (Ti[OCH(CH 3 ) 2 J 4 , Aldrich, 99.999%, 1OmL) was used as a precursor and mixed with 2-methoxyethanol (CH 3 OCH 2 CH 2 OH, Aldrich, 99.9+%, 5OmL) and ethanolamine (H 2 NCH 2 CH 2 OH, Aldrich, 99+%, 5mL) in a three-necked flask equipped connected with a condenser, thermometer, and argon gas inlet/outlet. Then, the mixed solution was heated to 80°C
• the typical TiO x precursor solution was prepared in isopropyl alcohol.
• P3HT/PCBM Ratio and Concentration The best device performance is achieved when the mixed solution had a P3HT/PCBM ratio of 1.0 : 0.8; i.e. with a concentration of P3HT(lwt%) plus PCBM(0.8wt%) in chlorobenzene.
• Polymer solar cells were prepared according to the following procedure: An ITO-coated glass substrate was first cleaned with detergent, then ultrasonicated in acetone and isopropyl, and subsequently dried in an oven overnight. Highly conducting poly(3,4-ethylenedioxylenethiophene)-polystyrene sulfonic acid (PEDOT:PSS, Baytron P) was spin-cast (5000 rpm) with thickness -40 nm from aqueous solution (after passing a 0.45 ⁇ m filter). The substrate was dried for 10 minutes at 140°C in air, and then moved into a glove box for spin-casting the photoactive layer.
• PEDOT:PSS polystyrene sulfonic acid
• the chlorobenzene solution comprised of P3HT (lwt%) plus PCBM (0.8wt%) was then spin-cast at 700 rpm on top of the PEDOT layer.
• the TiO x precursor solution in isopropanol was spin-cast in air on top of the polymer-fullerene composite layer.
• the precursor converts to TiO x by hydrolysis in the presence of ambient moisture.
• the sample was then heated at 150 0 C for 10 minutes inside a glove box filled with nitrogen. Subsequently the device was pumped down in vacuum ( ⁇ 10-7 torr), and a ⁇ 100 nm Al electrode was deposited on top.
• a suitable ZnO nanoparticle suspension can be formed using a sol-gel synthesis procedure for producing zinc oxide (ZnO) is as follows; zinc acetate dihydrate
• SVCA 31688.1 [Zn(CH 3 CO 2 ) 2 -2H 2 O, Aldrich, 98+%, lOmg] was dehydrated using about one hour in vacuum 120 0 C and mixed with 2-methoxyethanol (CH 3 OCH 2 CH 2 OH, Aldrich, 99.9+%, 5OmL) and ethanolamine (H 2 NCH 2 CH 2 OH, Aldrich, 99+%, 5mL) in a three-necked flask each connected with a condenser, thermometer, and argon gas inlet/outlet. Then, the mixed solution was heated to 8O 0 C for 2 hours in a silicon oil bath under magnetic stirring, followed by heating to 120°C for 1 hour.
• 2-methoxyethanol CH 3 OCH 2 CH 2 OH, Aldrich, 99.9+%, 5OmL
• ethanolamine H 2 NCH 2 CH 2 OH, Aldrich, 99+%, 5mL
• Fig. 5 shows a series of graphs showing the current density- voltage characteristics of representative polymer photovoltaic cells with and without representative zinc oxide optical spacers illuminated with 25 mW/cm 2 at 532 nm.
• the accuracy of the solar simulator at Konarka is based on standard cells traced to the National Renewable Energy Laboratory (NREL). Measurements were done with the solar cells inside the glove box by using a high quality optical fiber to guide the light from the solar simulator (outside the glove box). Current density- voltage curves were measured with a Keithley 236 source measurement unit.
• NREL National Renewable Energy Laboratory

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  • 2006-03-17 EP EP06836037A patent/EP1859495A1/en not_active Withdrawn
  • 2006-03-17 WO PCT/US2006/009987 patent/WO2007040601A1/en active Application Filing

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