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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...
Citations
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Journal ArticleDOI
TL;DR: In this article, the effect of plasmonic nanostructures on the multiexciton dynamics of a single CdSe/ZnS core/shell colloidal nanocrystal quantum dot was investigated.
Abstract: The change of photon statistics in the fluorescence of a single CdSe/ZnS core/shell colloidal nanocrystal quantum dot (NQD) accompanying the atomic force microscopy (AFM) manipulation of a cubic Au nanoparticle (AuCube) was investigated to elucidate the effect of plasmonic nanostructures on the multiexciton dynamics of the NQD. Upon coupling to an AuCube of a well-defined size and shape, we directly observed the conversion of a single-photon emission from an individual NQD to a multiphoton emission, and this was accompanied by an increase in fluorescence intensity and a reduction in fluorescence lifetime. The multiphoton emission then returned to a single-photon emission upon separating the AuCube from the single NQD. The efficiency of the multiphoton emission was enhanced 6.9 times through the use of the AuCube. The enhancement of the multiphoton emission was attributable mainly to the augmentation of the biexciton emission rate. These results provide evidence that quantum dot photon statistics can be ma...

38 citations

Journal ArticleDOI
TL;DR: In order to attach nanoparticles to substrates using solution based assembly methodologies, one invariably relies on linking molecules whose importance is not solely as the binding component betwee...
Abstract: In order to attach nanoparticles to substrates using solution based assembly methodologies, one invariably relies on linking molecules whose importance is not solely as the binding component betwee...

38 citations

Journal ArticleDOI
TL;DR: In this paper, a large number of dangling bonds are detected on the silicon nanocrystal (Si NC) surface after surface modification, and controlled particle oxidization is proposed as a substitution method for surface passivation, which can reduce carrier traps easily and effectively.

38 citations

Journal ArticleDOI
TL;DR: In this paper, the synthesis of monodispersed PbS nanocrystals by a facile chemical bath deposition and cost-effective approach is described, which can be easily controlled by varying the deposition time.
Abstract: This study describes the synthesis of monodispersed PbS nanocrystals by a facile chemical bath deposition and cost-effective approach. PbS counter electrodes (CEs) were used to grow high-quality thin films containing cube-shaped nanocrystals or nanodendrites. The size and shape of the PbS nanocrystals can be easily controlled by varying the deposition time. Quantum dot-sensitized solar cells (QDSSCs) were made and showed improved performance using the PbS CEs obtained with a deposition time of 2 h. The nanocrystal structured PbS CE in QDSSCs under one-sun illumination (AM 1.5, 100 mW cm−2) yielded a high short circuit current density (Jsc) of 11.20 mA cm−2, an open circuit voltage (Voc) of 0.560 V, a fill factor (FF) of 0.55, and a power conversion efficiency (η) of 3.48%. These values are much higher than those of the Pt CE (Jsc = 79.29 mA cm−2, Voc = 0.604, FF = 0.28, and η = 1.58%). The concentration of acetic acid plays an important role in deciding the size and shape of the PbS nanocrystals in the nucleation and growth process. The PbS strongly adhered to the FTO substrate due to the acetic acid, which acts as a stabilizer and a strong reagent in this one-step preparation. The performance of the PbS CE was improved by the surface morphology, which enables rapid electron transport and a lower electron recombination rate for the polysulfide electrolyte redox couple. Electrochemical impedance spectroscopy and Tafel-polarization measurements were used to investigate the electrocatalytic activity of the PbS and Pt CEs.

38 citations

Journal ArticleDOI
TL;DR: In this article, the effect of the photoanode structure over the performance of CdS/CdSe-cosensitized solar cells by comparing four types of photoanodes structures: nanocrystal film, blend film, bilayer film and PMSs film.
Abstract: TiO2 polydisperse mesoporous spheres (PMSs) and nanocrystals were selectively prepared via slightly altering the precursor dosage in a solvothermal reaction. Afterwards, the submicrometer-sized PMSs and nanocrystals were adopted as sample materials to shed light on the effect of the photoanode structure over the performance of CdS/CdSe-cosensitized solar cells by comparing four types of photoanode structures: nanocrystal film, blend film, bilayer film and PMSs film. It was found that the bilayer photoanode could promote the harvesting of incident light by increasing both the CdS/CdSe QDs loading amount and the scattering effect. According to the transient photovoltage measurements, the carrier recombination at the TiO2/electrolyte and FTO/electrolyte interfaces were substantially passivated in the bilayer cell. Moreover, a high electron diffusion rate of 142.0 × 10−9 m2 s−1 was also obtained in the bilayer cell, indicating high photoelectrons collection efficiency in the film structure. Therefore, the bilayer cell can well integrate the structural advantages of the PMSs and nanocrystals, which contributes to a high conversion efficiency of 4.70%, demonstrating a ∼54% and ∼12% improvement compared with the cells derived from nanocrystal and PMSs, respectively.

38 citations

References
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Journal ArticleDOI
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.

11,071 citations

Journal ArticleDOI
02 Aug 2002-Science
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.

9,693 citations

Journal ArticleDOI
15 Dec 1995-Science
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.

9,611 citations

Journal ArticleDOI
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

Journal ArticleDOI
25 Sep 1998-Science
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