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: In this paper, a review of plasmonic nanomaterials for the removal of contaminants and inactivation/killing of pathogenic microorganisms is presented, where a number of examples for the development of composite nanostructures are provided.
Abstract: Technologies based on nanomaterials are gaining increased attention as a promising method for the removal of contaminants and inactivation/killing of pathogenic microorganisms. Plasmonic nanomaterials prove to be promising in this field due to their tailored properties, including optical, photothermal, conducive, and catalytic properties. These properties have been widely used for the design of efficient materials for the environmental applications by improving the light absorption efficiency, redox reaction kinetic rates, and charge separation efficiency. In the current review, the tailored properties of plasmonic nanomaterials and how they are employed for the design of efficient environment-functional materials are discussed in detail. A number of examples for the development of composite plasmonic nanostructures such as metal/semiconductor, metal/insulator/semiconductor, and metal/semiconductor/semiconductor are provided. In addition, the recent achievements in plasmonic nanomaterials for the removal of contaminants (in both liquid and gaseous media) and the inactivation of pathogenic microorganisms are described with a number of examples. The major challenges in employing plasmonic nanomaterials for environmental applications are identified as: (1) complete mineralization of contaminants must be achieved in some cases due to the potential risks of intermediates; (2) the cost of plasmonic nanomaterials and the associated treatment processes need to be significantly decreased; (3) the stability of plasmonic nanomaterials in real environmental matrices is urgently needed to be improved; (4) the ecological safety of these nanomaterials should be investigated extensively. However, it is expected that with continuous progress of this field, plasmonic nanotechnology can be used for environmental applications more widely, not only for the examples shown in the current review, but also for soil remediation, resource recovery during waste treatment processes, and detection of contaminants. Finally, the toxicity of engineered plasmonic nanomaterials, the possibility of their release, fate, and transformation, in the environment and subsequent impact on the health of ecosystem are also addressed in detail.
136 citations
TL;DR: In this article, a linker assisted chemical bath deposition method was proposed to synthesize CdTe or cdTe/CdS quantum dot sensitized TiO2 photoelectrodes.
Abstract: We report on an interesting and efficient one-step linker assisted chemical bath deposition method to synthesise CdTe or CdTe/CdS quantum dot sensitized TiO2 photoelectrodes. The CdTe or CdTe/CdS core/shell quantum dots with different size and structure can be easily obtained by controlling the hydrothermal temperature. The QDs are covalently linked to TiO2 nanocrystallites by thioglycolic acid (TGA) bifunctional molecule which also acts as stabilizer and sulfur source in this one-step fabrication. In this sensitized electrode, CdTe has higher light absorptivity while the CdS shell plays a crucial role in the sensitive CdTe QDs protection and photo-generated charges separation. Both effects push the power conversion efficiency of the quantum dot sensitized solar cells (QDSSCs) up to 3.8% and 5.25% under AM 1.5 G one sun (100 mW cm−2) and 0.12 sun illumination, respectively.
136 citations
TL;DR: The chair conformers of both 3a and 3b are formed preferentially over their boat conformers due to the close proximity of the chelated bisphosphine platinum groups and the nature of the excited states for these metallosupramolecular rhomboids varies with the acetylene chain length of the donor ligands and with the different conformers.
Abstract: In this work, the photophysical properties of coordination-driven self-assembled metallosupramolecular rhomboids with the donor ligands 1,2-bis(3-pyridyl)ethyne (3a) and 1,4-bis(3-pyridyl)-1,3-butadiyne (3b) are investigated by use of both spectroscopic experiments and quantum chemistry calculations. All the geometric conformations of the chair and boat conformers of 3a and 3b are fully optimized using density functional theory. The time-dependent density functional theory method was also used to study the excited-state properties of these self-assembled metallosupramolecular rhomboids. At the same time, steady-state absorption and fluorescence as well as the time-correlated single photon counting techniques are used to measure their various spectral properties. The fluorescence spectra of these self-assembled metallosupramolecular rhomboids are very wide and show an evident two-peak feature, which can be tuned by different excitation wavelengths. It has been demonstrated that the chair conformers of both...
135 citations
TL;DR: The investigations showed a high resistivity for the QD/metal back contact, which reduces drastically under illumination, and a shift of the depletion layer capacitance under illumination related to the change of the dipole at this interface.
Abstract: Solid state PbS quantum dots (QDs)/TiO2 heterojunction solar cells were produced by depositing PbS QDs on a 500 nm thick mesoscopic TiO2 films using layer-by-layer deposition. Importantly, the PbS QDs act here as photosensitizers and at the same time as hole conductors. The PbS QDs/TiO2 device produces a short circuit photocurrent (Jsc) of 13.04 mA/cm2, an open circuit photovoltage (Voc) of 0.55 V and a fill factor (FF) of 0.49, corresponding to a light to electric power conversion efficiency (η) of 3.5% under AM1.5 illumination. The electronic processes occurring in this device were investigated by transient photocurrent and photovoltage measurements as well as impedance spectroscopy in the dark and under illumination. The investigations showed a high resistivity for the QD/metal back contact, which reduces drastically under illumination. EIS also indicated a shift of the depletion layer capacitance under illumination related to the change of the dipole at this interface.
135 citations
TL;DR: Cysteine, a sulfur-containing nonessential amino acid, plays a critical role in many biological processes and contributes towards enzymatic reactions and detoxifi cation processes, and participates in numerous posttranslational modifi cations.
Abstract: As a fundamental building block for functional and structural components of many proteins and enzymes, cysteine, a sulfur-containing nonessential amino acid, plays a critical role in many biological processes. [ 1 ] This critical residue helps to fold and maintain a stable structure of protein, contributes towards enzymatic reactions and detoxifi cation processes, and participates in numerous posttranslational modifi cations. [ 2 ]
135 citations
References
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TL;DR: In this article, an upper theoretical limit for the efficiency of p−n junction solar energy converters, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of holeelectron pairs is radiative as required by the principle of detailed balance.
Abstract: In order to find an upper theoretical limit for the efficiency of p‐n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole‐electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction fc of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and fc as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000°K and 300°K, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and fc = 1. Actual junctions do not obey the predicted current‐voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.
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TL;DR: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects.
Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.
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TL;DR: In this paper, the carrier collection efficiency and energy conversion efficiency of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives.
Abstract: The carrier collection efficiency (ηc) and energy conversion efficiency (ηe) of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives. Composite films of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) and fullerenes exhibit ηc of about 29 percent of electrons per photon and ηe of about 2.9 percent, efficiencies that are better by more than two orders of magnitude than those that have been achieved with devices made with pure MEH-PPV. The efficient charge separation results from photoinduced electron transfer from the MEH-PPV (as donor) to C60 (as acceptor); the high collection efficiency results from a bicontinuous network of internal donor-acceptor heterojunctions.
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TL;DR: In this paper, the authors describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment.
Abstract: The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...
9,086 citations
TL;DR: Semiconductor nanocrystals prepared for use as fluorescent probes in biological staining and diagnostics have a narrow, tunable, symmetric emission spectrum and are photochemically stable.
Abstract: Semiconductor nanocrystals were prepared for use as fluorescent probes in biological staining and diagnostics. Compared with conventional fluorophores, the nanocrystals have a narrow, tunable, symmetric emission spectrum and are photochemically stable. The advantages of the broad, continuous excitation spectrum were demonstrated in a dual-emission, single-excitation labeling experiment on mouse fibroblasts. These nanocrystal probes are thus complementary and in some cases may be superior to existing fluorophores.
8,542 citations