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 study of CZTS nanoparticles synthesized by solvothermal method using five different solvents (Water, ethanol, Diethylene glycol, Ethylene diamine, and ethanol) is reported.
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TL;DR: Field-effect transistors are fabricated from thin films of Ag-doped PbSe nanocrystals to analyze the influence of electronically active impurities on electrical transport in this important material for nanocrystal applications.
Abstract: Field-effect transistors are fabricated from thin films of Ag-doped PbSe nanocrystals to analyze the influence of electronically active impurities on electrical transport in this important material for nanocrystal applications. Data is collected as a function of nanocrystal size, dopant concentration, and temperature. Changes in the Fermi level and transport parameters indicate that Ag is acting as a p-type dopant (acceptor).
53 citations
TL;DR: In this paper, the authors demonstrate an optimized dual sensitization strategy that combines the linker-assisted self-assembly of QDs and successive ionic layer adsorption and reaction (SILAR) approach to assemble high-efficiency QDSCs.
Abstract: The potential of quantum-dot sensitized solar cells (QDSCs), a promising candidate for third-generation photovoltaics, has not been fully realized with the corresponding power conversion efficiencies (PCE) still hovering below 9%. In this context, we demonstrate an optimized dual sensitization strategy that combines the linker-assisted self-assembly of QDs and successive ionic layer adsorption and reaction (SILAR) approach to assemble high-efficiency QDSCs. CdTe/CdS core/shell QDSC is chosen as the model system whose PCE, so far, has been reported at ∼3.8%. Our dual sensitization strategy comprises self-assembly of Type-II CdTe/CdS core/shell QDs on porous TiO2 followed by deposition of an additional CdS quasi-shell through SILAR. The highest QD surface coverage was optimized by systematic pH variation, whereby PCE improved from 2.04(1)% (pH 11) to 3.696(5)% (pH 13). It was observed that while the epitaxial shell passivates the core surface traps, the nonepitaxial quasi-shell passivates the TiO2 surface s...
53 citations
TL;DR: In this paper, the in situ preparation of high-quality organically synthesized cadmium selenide (CdSe) nanocrystals on TiO2 nanotubes (T_NT) prepared by anodization is presented.
Abstract: The in situ preparation of high-quality organically synthesized cadmium selenide (CdSe) nanocrystals on TiO2 nanotubes (T_NT) prepared by anodization is presented. The deposition of CdSe nanocrystals has been facilitated under a high-pressure and low-viscosity solvothermal process. The formation, growth, and assembly of CdSe nanocrystals in the form of a dense film on T_NT have been studied using thermal (thermogravimetry and calorimetry) and optical (UV–vis and microscopy) techniques. It has been concluded that an organic treatment, followed by annealing under a nitrogen atmosphere at reduced temperatures, helps control CdSe nanocrystal morphology without causing significant particle size growth. Photoelectrochemical measurements indicate that the electrode assembly consisting of T_NT and CdSe can achieve a stable photocurrent density of 6.7 mA/cm2 and a charge-separation efficiency of 35%.
53 citations
TL;DR: In this paper, a femtosecond ablation of bulk Si target in acetone was performed with ∼40 fs (fwhm) pulses and different input energies of ∼500, ∼200, ∼150, ∼100, ∼50, and ∼10 μJ.
Abstract: Silicon (Si) nanoparticles (NPs) and self-organized high spatial frequency laser (HSFL) induced periodic surface structures were fabricated by means of femtosecond ablation of bulk Si target in acetone. The ablation was performed with ∼40 fs (fwhm) pulses and different input energies of ∼500, ∼200, ∼150, ∼100, ∼50, and ∼10 μJ. Fabricated NPs and nanostructures (NSs) were characterized by UV–visible absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. The average sizes of the NPs were estimated to be in the 4–135 nm range. From the PL studies of Si NPs of different sizes, we have observed a size-dependent shift toward blue spectral region. We could tune the observed PL peak in the spectral range of 440–515 nm. The crystalline and amorphous nature of the Si nanoparticles and nanostructures was investigated using selected area electron diffraction and Raman spectra. Complex refractive index, conduc...
52 citations
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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.
9,693 citations
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
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...
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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