scispace - formally typeset
Search or ask a question
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
More filters
Journal ArticleDOI
TL;DR: In this article, a polystyrene-modified TiO2 film (M-TiO2) with micro-cluster structure, containing micro/nano-composite pores is obtained after sintering.

36 citations

Journal ArticleDOI
TL;DR: Without the oxidation of TOPO, CdSe quantum dots (QDs) were synthesized instead, and this discovery reinforces the efficacy of DOPA and OPA molecules as critical ligands in the formation of 1-dimensional (1D) nanostructures.
Abstract: In-situ TOPO decomposition was accomplished by applying a vacuum at elevated temperatures to a precursor solution in the presence of oxygen, leading TOPO to oxidize to di-n-octylphosphinic acid (DOPA) and octylphosphonic acid (OPA). The mixed ligand system of tetradecylphosphonic acid (TDPA), DOPA and OPA produced CdSe QRs on the order of 4 nm in diameter and 20 nm in length. Solvent and ligand identification was performed by mass spectrometry and (31)P nuclear magnetic resonance spectroscopy. Transmission electron microscopy (TEM) was utilized to determine the morphology, size and crystal growth of the CdSe QRs. This method of CdSe QR synthesis is unique in that the phosphonic acids responsible for anisotropic growth are formed in situ, prior to the nucleation and growth of the nanorods. Without the oxidation of TOPO, CdSe quantum dots (QDs) were synthesized instead, as reported previously. This discovery reinforces the efficacy of DOPA and OPA molecules as critical ligands in the formation of 1-dimensional (1D) nanostructures.

36 citations

Journal ArticleDOI
TL;DR: It is concluded that the charge-separation efficiency of rutileTiO2 is enhanced relative to that of anatase TiO2 upon the deposition of Pt nanoparticles.
Abstract: Absorption spectra of anatase and rutile TiO2 in the 150–300 nm region before and after the deposition of Pt nanoparticles were measured. For anatase TiO2, the spectral intensity in the longer wavelength region decreased (>∼210 nm), while that in the shorter wavelength region increased (<∼210 nm). In particular, spectral band intensity in the far-ultraviolet (FUV) region (∼160 nm) was increased. In contrast, the spectral intensity of rutile TiO2 increased over the entire wavelength region under investigation. Rutile TiO2 showed a spectral band at a longer wavelength region (∼170 nm) than anatase TiO2, and the difference in the band wavelengths in the FUV region was due to the differences in the electronic structures of their phase. The decrease and increase in the intensity upon the Pt nanoparticle deposition suggest electron transfer from the TiO2 to Pt nanoparticles and enhancement of charge-separation, respectively. The photocatalytic activity of rutile TiO2, as evaluated by a photo-degradation reaction of methylene blue, increased more than that of anatase TiO2 upon the deposition of Pt nanoparticles. Thus, we concluded that the charge-separation efficiency of rutile TiO2 is enhanced relative to that of anatase TiO2 upon the deposition of Pt nanoparticles.

36 citations

Journal ArticleDOI
TL;DR: In this article, highly conductive CdS inverse opal structures are prepared via a multistep process, where the backbones are first built up on conductive glass substrates via co-deposition of CdSe quantum dots and polystyrene microspheres, followed by calcination, after which subsequent electrodepositon and annealing treatments are applied to transform the fine constituent nanocrystals into larger ones, thus considerably enhancing the electrical conductivity.
Abstract: Semiconductor materials with an inverse opal structure have previously demonstrated promise for photovoltaic applications. However, their use in solar cells is still restricted by their poor electron transfer properties. Here, highly conductive CdS inverse opal structures are prepared via a multistep process, where CdS inverse opal backbones are first built up on conductive glass substrates via co-deposition of CdS quantum dots and polystyrene microspheres, followed by calcination, after which subsequent electrodepositon and annealing treatments are applied to transform the fine constituent nanocrystals into larger ones, thus considerably enhancing the electrical conductivity. The obtained CdS networks are tested as anodes in photochemical solar cells and demonstrate conversion efficiency values up to 2.00% under the illumination of one sun. After depositing an additional CdSe layer, the conversion efficiency of the structures is further increased to 2.47%.

36 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss QDs with various semiconductor compositions and describe the mechanisms behind the operation of QDs and QLEDs and the primary strategies for improving their photoluminescence (PL) quantum yield (QY) and stability.
Abstract: The development of quantum dots (QDs) has had a significant impact on various applications, such as solar cells, field-effect transistors, and light-emitting diodes (LEDs). Through successful engineering of the core/shell heterostructure of QDs, their photoluminescence (PL) quantum yield (QY) and stability have been dramatically enhanced. Such high-quality QDs have been regarded as key fluorescent materials in realizing next-generation display devices. Particularly, electrically driven (or electroluminescent, EL) QD light-emitting diodes (QLED) have been highlighted as an alternative to organic light-emitting diodes (OLED), mostly owing to their unbeatably high color purity. Structural optimizations in QD material as well as QLED architecture have led to substantial improvements of device performance, especially during the past decade. In this review article, we discuss QDs with various semiconductor compositions and describe the mechanisms behind the operation of QDs and QLEDs and the primary strategies for improving their PL and EL performances.

36 citations

References
More filters
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