Quantum dot sensitization of organic-inorganic hybrid solar cells
16 Jul 2002-Journal of Physical Chemistry B (American Chemical Society)-Vol. 106, Iss: 31, pp 7578-7580
TL;DR: A high surface area pn-heterojunction between TiO2 and an organic p-type charge transport material (spiro-OMeTAD) was sensitized to visible light using lead sulfide (PbS) quantum dots as mentioned in this paper.
Abstract: A high surface area pn-heterojunction between TiO2 and an organic p-type charge transport material (spiro-OMeTAD) was sensitized to visible light using lead sulfide (PbS) quantum dots. PbS quantum dots were formed in situ on a nanocrystalline TiO2 electrode using chemical bath deposition techniques.1 The organic hole conductor was applied from solution to form the sensitized heterojunction. The structure of the quantum dots was analyzed using HRTEM technique. Ultrafast laser photolysis experiments suggested the initial charge separation to proceed in the subpicosecond time range. Transient absorption laser spectroscopy revealed that interfacial charge recombination of the initially formed charge carriers is much faster than in comparable dye-sensitized systems.2,3 The sensitized heterojunction showed incident photon-to-electron conversion efficiencies (IPCE) of up to 45% and energy conversion efficiencies under simulated sunlight AM1.5 (10 mW/cm2) of 0.49%.
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TL;DR: Two organolead halide perovskite nanocrystals were found to efficiently sensitize TiO(2) for visible-light conversion in photoelectrochemical cells, which exhibit strong band-gap absorptions as semiconductors.
Abstract: Two organolead halide perovskite nanocrystals, CH3NH3PbBr3 and CH3NH3PbI3, were found to efficiently sensitize TiO2 for visible-light conversion in photoelectrochemical cells. When self-assembled on mesoporous TiO2 films, the nanocrystalline perovskites exhibit strong band-gap absorptions as semiconductors. The CH3NH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The CH3NH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%.
16,634 citations
TL;DR: The use of a solid hole conductor dramatically improved the device stability compared to (CH3NH3)PbI3 -sensitized liquid junction cells.
Abstract: We report on solid-state mesoscopic heterojunction solar cells employing nanoparticles (NPs) of methyl ammonium lead iodide (CH3NH3)PbI3 as light harvesters. The perovskite NPs were produced by reaction of methylammonium iodide with PbI2 and deposited onto a submicron-thick mesoscopic TiO2 film, whose pores were infiltrated with the hole-conductor spiro-MeOTAD. Illumination with standard AM-1.5 sunlight generated large photocurrents (JSC) exceeding 17 mA/cm2, an open circuit photovoltage (VOC) of 0.888 V and a fill factor (FF) of 0.62 yielding a power conversion efficiency (PCE) of 9.7%, the highest reported to date for such cells. Femto second laser studies combined with photo-induced absorption measurements showed charge separation to proceed via hole injection from the excited (CH3NH3)PbI3 NPs into the spiro-MeOTAD followed by electron transfer to the mesoscopic TiO2 film. The use of a solid hole conductor dramatically improved the device stability compared to (CH3NH3)PbI3 -sensitized liquid junction cells.
6,751 citations
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03 Aug 2010TL;DR: The dye-sensitized solar cells (DSC) as discussed by the authors provides a technically and economically credible alternative concept to present day p-n junction photovoltaic devices, where light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor.
Abstract: The dye-sensitized solar cells (DSC) provides a technically and economically credible alternative concept to present day p–n junction photovoltaic devices. In contrast to the conventional systems where the semiconductor assume both the task of light absorption and charge carrier transport the two functions are separated here. Light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the solid. Carriers are transported in the conduction band of the semiconductor to the charge collector. The use of sensitizers having a broad absorption band in conjunction with oxide films of nanocrstalline morphology permits to harvest a large fraction of sunlight. Nearly quantitative conversion of incident photon into electric current is achieved over a large spectral range extending from the UV to the near IR region. Overall solar (standard AM 1.5) to current conversion efficiencies (IPCE) over 10% have been reached. There are good prospects to produce these cells at lower cost than conventional devices. Here we present the current state of the field, discuss new concepts of the dye-sensitized nanocrystalline solar cell (DSC) including heterojunction variants and analyze the perspectives for the future development of the technology.
4,159 citations
TL;DR: Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each that are among the hottest research topics of the last decades.
Abstract: Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389
3,720 citations
TL;DR: Developing solar cells that are based on the sensitization of mesoscopic oxide films by dyes or quantum dots, and the examples for the first outdoor application of such solar cells will be provided.
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...
3,214 citations
References
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TL;DR: A dye-sensitized heterojunction of TiO2 with the amorphous organic hole-transport material 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene (OMeTAD) was described in this article.
Abstract: Solar cells based on dye-sensitized mesoporous films of TiO2 arelow-cost alternatives to conventional solid-state devices1. Impressive solar-to-electrical energy conversion efficiencies have been achieved with such films when used in conjunction with liquid electrolytes2. Practical advantages may be gained by the replacement of the liquid electrolyte with a solid charge-transport material. Inorganic p-type semiconductors3,4 and organic materials5,6,7,8,9 have been tested in this regard, but in all cases the incident monochromatic photon-to-electron conversion efficiency remained low. Here we describe a dye-sensitized heterojunction of TiO2 with the amorphous organic hole-transport material 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene (OMeTAD; refs. 10 and 11). Photoinduced charge-carrier generation at the heterojunction is very efficient. A solar cell based on OMeTAD converts photons to electric current with a high yield of 33%.
3,386 citations
TL;DR: In this article, the photocurrent quantum yield reached values of more than 70% for Q-CdS and Q-PbS sensitized electrodes, while the amount of light absorption is negligibly small.
Abstract: In semiconductor particles of nanometer size, a gradual transition from solid state to molecular structure occurs as the particle size decreases. In this very size regime, the physical and chemical properties of the particlesstrongly depend on their size.14 One of the first utilizations of the fascinating properties of these quantum-sized particles (Q-particles) for typical semiconductor applications was to embed the particles into porous Ti02 films and to use those modified layers as light-converting electrodesael Visible light was absorbed by theQ-particles which, consequently, transferred electrons into the porous Ti02 substrate. The photocurrent quantum yield reached values of more than 70% for Q-CdS and Q-PbS sensitized electrodes. Similar results were also obtained in a later work by Hotchandani and KamatI2 with Q-CdS on ZnO electrodes, who measured quantum yields of up to 15%. The basic principle of theseelectrodes, namely, the sensitization of a wide-bandgap semiconductor, has been investigated intensively during the past 3 decades whereby organic dyes were used as sen~itizers.~~15 Low coverage of the semiconductor surface by the dye molecules, typically much less than a monolayer, was found as a requirement for an effective charge carrier separation. Under these conditions, however, the amount of light absorption is negligibly small. A few years ago, a remarkable advance was made by Grltzel and co-workers, who used a highly porous Ti02 substrate electrode with a tris(bipyridy1)ruthenium or a coumarine dye as sensitizer.1618 The internal surface area of these electrodes was so large that less than a monolayer of adsorbed dye molecules was already sufficient for total light absorption. Electrochemical cells based on these electrodes are currently being discussed as a possible, cheap alternative to amorphous silicon solar cells. The crucial part in the cells is the dye itself only a very limited number of dyes give high photocurrent quantum yields and are reasonably stable against photodegradation. As already pointed out: the use of Q-particles as sensitizers principally implies several advantages as compared to organic dyes: the bandgap and thereby the absorption range are easily adjustable by the size of the particles, the band edge type of absorption behavior is most favorable for effective light harvesting, and the surface properties of the particles can be modified in order to increase the photostability of the electrodes. In contrast to organic dyes, however, the photophysics and photochemistry of Q-particles are still only poorly understood, and most of the knowledge is empirically based. Experiments on Q-particle sensitization are, therefore, still considered more at a level of basic research than at a level of practical application.
1,023 citations
TL;DR: In this paper, a photoelectrochemical cell was formed that consisted of p-type InP QDs loaded on TiO2, which was immersed in a I-/I3- or hydroquinone/quinone acetonitrile solution, and a Pt counter electrode.
Abstract: Quantum dots (QDs) of InP strongly adsorb onto transparent, porous, nanocrystalline TiO2 electrodes prepared by sintering 200−250 A diameter TiO2 colloidal particles. The interparticle space of the TiO2 electrodes is large enough to permit deep penetration of 65-A InP QDs into the porous TiO2 film. The absorption of light increases linearly with the thickness of the TiO2 film indicating that the InP QDs are adsorbed homogeneously on the TiO2 surface. We found that large particles adsorb better than smaller ones probably due to less hindrance by the stabilizer. The solid films exhibit strong photoconductivity in the visible region indicating photosensitization of TiO2 by InP QDs. The photocurrent action spectrum of the TiO2/InP QD film at a potential of +1 V is consistent with the absorption spectrum of the InP QDs. A photoelectrochemical cell was formed that consisted of p-type InP QDs loaded on TiO2, which was immersed in a I-/I3- or hydroquinone/quinone acetonitrile solution, and a Pt counter electrode....
556 citations
TL;DR: In this paper, the performance of dye-sensitized solar cells based on spiro-MeOTAD was improved by controlling charge recombination across the interface of the heterojunction.
Abstract: The performance of solid-state dye-sensitized solar cells based on spiro-MeOTAD was considerably improved by controlling charge recombination across the interface of the heterojunction. This was achieved by blending the hole conductor matrix with a combination of 4-tert-butylpyridine (tBP) and Li[CF3SO2]2N. Open circuit voltages Uoc over 900 mV and short circuit currents Isc up to 5.1 mA were obtained, yielding an overall efficiency of 2.56% at AM1.5 illumination. These values have been fully confirmed at the National Renewable Energy Laboratories for a device with an active area of 1.07 cm2, signifying a dramatic improvement compared to previously reported values for a similar device.
485 citations
TL;DR: In this article, a comparison of optical and photoelectrochemical properties of the TiO2 layer indicates a relative enhancement of light harvesting efficiency due to lowering of reflection losses in the electrolyte.
417 citations