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Journal ArticleDOI

Quantum Dot Solar Cells. Semiconductor Nanocrystals as Light Harvesters

18 Oct 2008-Journal of Physical Chemistry C (American Chemical Society)-Vol. 112, Iss: 48, pp 18737-18753
TL;DR: In this paper, three major ways to utilize semiconductor dots in solar cell include (i) metal−semiconductor or Schottky junction photovoltaic cell, (ii) polymer−smiconductor hybrid solar cell, and (iii) quantum dot sensitized solar cell.
Abstract: The emergence of semiconductor nanocrystals as the building blocks of nanotechnology has opened up new ways to utilize them in next generation solar cells. This paper focuses on the recent developments in the utilization of semiconductor quantum dots for light energy conversion. Three major ways to utilize semiconductor dots in solar cell include (i) metal−semiconductor or Schottky junction photovoltaic cell (ii) polymer−semiconductor hybrid solar cell, and (iii) quantum dot sensitized solar cell. Modulation of band energies through size control offers new ways to control photoresponse and photoconversion efficiency of the solar cell. Various strategies to maximize photoinduced charge separation and electron transfer processes for improving the overall efficiency of light energy conversion are discussed. Capture and transport of charge carriers within the semiconductor nanocrystal network to achieve efficient charge separation at the electrode surface remains a major challenge. Directing the future resear...
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TL;DR: This work reviews the historical development of Transition metal dichalcogenides, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.
Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

13,348 citations

Journal ArticleDOI
TL;DR: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency as mentioned in this paper, and many DSC research groups have been established around the world.
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 ...

8,707 citations

Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: In this paper, the development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed.
Abstract: Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 structure, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photoelectrochemical methods. Various applications of VLA TiO2, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO2 are discussed and compared to conventional UV-activated TiO2 nanomaterials. Recent advances in bacterial disinfection using VLA TiO2 are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted.

3,305 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discussed the steps that have led to this discovery, and the future of this rapidly advancing concept have been considered, and it is likely that the next few years of solar research will advance this technology to the very highest efficiencies while retaining the very lowest cost and embodied energy.
Abstract: Over the last 12 months, we have witnessed an unexpected breakthrough and rapid evolution in the field of emerging photovoltaics, with the realization of highly efficient solid-state hybrid solar cells based on organometal trihalide perovskite absorbers. In this Perspective, the steps that have led to this discovery are discussed, and the future of this rapidly advancing concept have been considered. It is likely that the next few years of solar research will advance this technology to the very highest efficiencies while retaining the very lowest cost and embodied energy. Provided that the stability of the perovskite-based technology can be proven, we will witness the emergence of a contender for ultimately low-cost solar power.

2,506 citations

References
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Journal ArticleDOI
TL;DR: This result indicates that Ru complexes can be sensitized by CdSe NQDs, which opens interesting opportunities for designing new types of photocatalytic materials for solar energy conversion applications.
Abstract: In this communication, we demonstrate a new approach to sensitization of Ru−polypyridine complexes by using semiconductor nanocrystal quantum dots (NQDs). When mixed in solution, the complexes functionalized by carboxylic groups adsorb onto the surface of the NQDs. Excitation of NQDs by 400 nm light leads to fast, 5 ps hole transfer from the photoexcited NQDs to the surface-adsorbed complexes. This result indicates that Ru complexes can be sensitized by CdSe NQDs, which opens interesting opportunities for designing new types of photocatalytic materials for solar energy conversion applications. These materials will take advantage of broad size-controlled absorption spectra and large extinction coefficients of NQDs as well as the unique property of NQDs to respond to absorption of a single photon by producing multiple electron−hole pairs.

217 citations

Journal ArticleDOI
TL;DR: In this article, photoexcited CdS/TiO2 composite system was investigated using emission and transient absorption spectroscopy, and the particle sizes of the two components were controlled by varying water-to-surfactant molar ratio, with values of 1, 2.5, 5 and 10.
Abstract: Photoinduced electron transfer in a size-quantized CdS/TiO2 composite system has been investigated using emission and transient absorption spectroscopy. Quantum-sized CdS and TiO2 particles were synthesized in reverse micelles using di-octyl sulfosuccinate (Aerosol-OT, AOT) as the surfactant stabilizer. The particle sizes of CdS and TiO2 were controlled by varying water-to-surfactant molar ratio, wo = [H2O]/[AOT], with values of 1, 2.5, 5 and 10. The blue-shift in the absorption onset confirmed size-quantization of these semiconductor particles. Electron transfer from photoexcited CdS to TiO2 was found to depend on the particle size of TiO2, where charge transfer was observed only when TiO2 particles were sufficiently large (>12 A). Interactions with smaller size TiO2 particles (⩽10 A) with CdS instead led to enhancements in emission with an increase in quantum yield from 2.3% to 8.8%. Picosecond laser flash photolysis experiments have been carried out to elucidate the interparticle electron transfer processes in the CdS/TiO2 reverse micellar system.

207 citations

Journal ArticleDOI
TL;DR: In this article, a general procedure is described for the attachment to antimony-doped tin dioxide (Sb), tin doped indium oxide (In203:Sn), or glass surfaces of molecules with known electron transfer or excited state properties.
Abstract: A general procedure is described for the attachment to antimony-doped tin dioxide (Sn02:Sb), tin-doped indium oxide (In203:Sn), or glass surfaces of molecules with known electron transfer or excited state properties, e.g. [Ru(bpy)2(4,4’-(CO~H)zbpy)] (PF6)2 (bpy = 2,2’-bipyridine, 4,4’-(COzH)zbpy = 4,4’-dicarboxy-2,2’-bipyridine), based on the interaction between surface hydroxyls and carboxylic acid groups. Integrations of cyclic voltammetric waveforms on the metal oxide electrodes give maximum surface coverages of r 1 X 10-10 mol/cm2 for the ruthenium complex, which corresponds to a monolayer coverage. Atomic force microscope (AFM) measurements reveal that the metal oxide surfaces are highly roughened with root mean square roughnesses in the range 4-6.5 nm for tin oxide. The smaller organics, N-methyl-N-viologenpropanoic acid bis(hexafluorophosphate), [MVC02H] (PF6)2, and 1 OH-phenothiazine10-propanoic acid, PTZ-C02H, display similar surface coverages. Resonance Raman measurements on surfaces containing the ruthenium complex imply that attachment to SnO2, In203, and Ti02 is via an ester bond. For ,902, two modes of binding are suggested, a majority by a chelating carboxylato link and a minority by ester formation. Binding constants for surface attachment were measured in CH2Cl2 at 298 K by equilibration, which gave K = 8 X lo4 M-’ on both SnO2:Sb and InzO3:Sn. Surface molecular assemblies have been prepared containing [ Ru( bp y ) 2(4,4’(COzH)2bpy)] (PF6) 2 and [Os( bpy) 2( 4,4’(CO2H)2 bpy ) ] (PF6) 2, [ MVCO#)(PF6)2, and PTZ-CO2H. In these assemblies, separate waves are observed for the different redox couples at potentials near those found for surfaces containing only a single component. Emission decay of the metal-toligand charge transfer (MLCT) excited state of [Ru(bpy)2(4,4’-(CO~H)2bpy)](PF6)2 attached to the glass backings of metal oxide electrodes or to glass slides was found to be nonexponential with average lifetimes (( 7 ) ) from < 5 to 600 ns with CHzCl2 in the external solution. ( T ) increases as surface coverage decreases. There is evidence for excited stateground state interactions by a red-shift in the emission maximum as surface coverage increases. Emission decay remains nonexponential even on surfaces that are lightly covered. Emission is nearly completely quenched on the semiconductor surfaces, with ( T ) < 5 ns. The bound Ru(I1) emitters on glass were quenched by electron or energy transfer to the coattached quenchers [MV-C02H] (PF& FTZ-C02H, or [Os(bpy)2(4,4’-(C02H)zbpy)] (PF& suggesting that lateral electron and energy transfer can occur across the surface. Surface lifetime quenching also occurred in the presence of added 10-methyl-10-phenothiazene in the external CH2Cl2 solution. The kinetics of lifetime quenching did not follow Stern-Volmer kinetics but could be fit to a model in which there are both quenchable and unquenchable sites on the same surface.

206 citations

Journal ArticleDOI
TL;DR: In this paper, the authors showed that adding butylamine to a solution of colloidal CdSe nanoparticles (NPs) caused a decrease in fluorescence intensity, with no effect on the picosecond bleach recovery of the exciton formation or on the luminescence dynamics.
Abstract: Addition of butylamine to a solution of colloidal CdSe nanoparticles (NPs) caused a decrease in fluorescence intensity, with no effect on the picosecond bleach recovery of the exciton formation or on the luminescence dynamics. The relative fluorescence quantum yield was found to decrease with increasing butylamine concentration and to level off at high concentrations, but the fluorescence lifetimes were not influenced. The nonlinear concentration dependence of the fluorescence quantum yield did not follow the Stern−Volmer equation. This is in agreement with the observation that the CdSe luminescence lifetime was not affected by the addition of butylamine. A mechanism is proposed in which the emission observed in CdSe is assumed to result from the combination of surface-trapped electrons and holes. n-Butylamine occupies hole sites, thus blocking the recombination process, which results in decreasing the density of luminescent centers. These results will be discussed in terms of the nature of the binding si...

206 citations