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2015, Solar Cells - New Approaches and Reviews
AI
Quantum dots (QDs) represent a promising advancement in solar cell technology due to their ability to have a tunable bandgap and potential for multiple exciton generation. These nanocrystals enhance efficiency by allowing for greater absorption of the solar spectrum compared to conventional silicon solar cells. The paper provides an overview of the physics, design, and synthesis techniques of QD solar cells, explores various architectures, and discusses the challenges and opportunities in this emerging field.
2024
Quantum Dot Solar Cells (QDSCs) are a promising technology in the field of photovoltaics, leveraging the unique properties of quantum dots to enhance solar energy conversion. QDSCs can be engineered to absorb a broad spectrum of light by tuning the size of the quantum dots, which improves their theoretical efficiency potential. Current laboratory efficiencies for QDSCs have reached around 16.6%, although practical, commercially viable efficiencies are generally lower. Their lightweight and flexible nature makes them suitable for a variety of applications, including portable solar devices and integration into unconventional surfaces like windows and clothing. Moreover, QDSCs have potential in tandem solar cells, where they can be paired with other cell types to achieve higher overall efficiencies. However, challenges such as long-term stability, scalability, and the use of toxic materials like lead need to be addressed before widespread commercialization[1].
Current Science
Owing to their versatile optical and electrical properties, semiconductor quantum dots are attracting attention as a material of choice for solar energy conversion. The quantum dot sensitized solar cells are considered as one of the most promising nextgeneration solar cells as they have the advantage of tunable band-gap energy and multiple exciton generation. We present here a study on quantum dot sensitized solar cells considering their construction and working, impact of incorporation of nanomaterials in solar cells and various structures for improving the performance of solar cells.
SPIE Newsroom, 2014
International Journal of Electrical and Computer Engineering (IJECE), 2020
This paper proposal new structure for improving the optical, electrical characteristics and efficiency of 3 rd generation heterojunction quantum dot solar cell (HJQDSC) (ITO/CdS/QDPbS/Au) model by using the quantum dot window layer instead of bulk structure layers cell. Also, this paper presents theoretically analysis for the performance of the proposal HJQDSC (ITO/QDCdS/QDPbS/Au) structure. The new design structure was applied on traditional (SnO2/CdS/CdTe/Cu) and (ZnO/CdS/CIGS/Mo) thin film solar cells which based on sub-micro absorber layer thickness models by replacing the bulk CdTe, CIGS absorber layers and CdS window layer with quantum dot size materials to achieve higher efficiency with lesser usage layer material. Also, it has been studied the effect of using semiconductors layers in quantum dots size on electric and optical properties of thin film solar cells and the effect of window and absorber layers quantum dots radii on the performance of solar cells. Finally, a thermal efficiency analysis has been investigated for explaining the importance of new structure HJQD solar cells. 1. INTRODUCTION Several solar technologies including wafer, thin film and organic, have been researched to achieve reliability, cost-effectiveness and high efficiency. Cost effectiveness can be seen in the use of less material as well as increasing energy conversion efficiency. The reduction in the efficiencies of the previous models due to the reduction of absorber layers thickness are associated with a number of problems [1-3]. The 3 rd generation of solar cells technique based on novel absorber layer materials with tunable bandgap that can be tuned to match the spectral distribution of solar spectrum are crucial and achieved less consummation absorber layer material. Quantum dots have the merit of tunable bandgap as a result of size variation as well as formation of intermediate bands. The energy band gap increases with a decrease in size of the quantum dot, the adjustable bandgap of quantum dots allows the construction of nanostructured solar cell that is able to harvest more of the solar spectrum [4]. Quantum dots can generate multiple exciton (electron-hole pairs) after collision with one photon of energy exceeding the band gap. Absorption of UV photons in quantum dots produces more electrons than near infrared photons. Quantum dots emit up to three electrons per photon due to multiple exciton generation as opposed to only one for standard crystalline silicon solar cell [5]. The previous study for heterojunction solar cells based on PbS-QDs/CdS thin films demonstrating an achieved efficiency of 3.3% [6].
Renewable Energy and Sustainable Buildings, 2019
Quantum dots (QDs) are semiconductor material with nano-crystal characterized by high absorption coefficient, retention time and re-emission in a desired direction with tunable spectrum. These characteristics render QDs favorable for concentrating solar radiation in the desired direction to form a quantum dot solar concentrators (QDSC). The extent of absorption and re-emission determines their effectiveness as concentrators. The QD effectiveness is influenced by type, shape, size, dot concentration and optical path length through the device. In order to optimize design of QDSC, the optimum doping concentration of QD in the QDSC devices is crucial. QDSC can be integrated to solar cells to improve PV integration and penetration to buildings. The QDSC embedded into glazing can help harvest solar energy by PV cells without affecting the occupants’ visual communication to outdoors thereby embodying energy producing transparent glazing. The aim of this paper is to review state of the art ...
International Journal of Scientific Research in Science and Technology, 2021
Owing to their versatile electro-optic properties semiconductor quantum dots (QDs) are gaining greater attention towards photovoltaic applications. Although hybrid solar cells, which are obtained by the blend of carbon-based and inorganic resources have the probable to attain higher energy conversion efficiencies, the current efficiencies are stumpy. Strategy aspects especially the electronic structure of the inanimate materials which are used as the electronic acceptors in mixture solar cells plays an important role in providing good performance. Among the four major inorganic material types which were scrutinized namely cadmium mixtures, silicon, metallic oxide nano particles besides short band gap nanoparticles, Cadmium Sulphide (CdS) quantum dots are having higher (>4%) power conversion efficiencies. As far as the academic and industrial communities are concerned, dye -sensitized solar cell has attained high priority in accordance with its good efficiencies, ease in manufacturing, low cost etc., Despite the above-mentioned advantages or the positive characteristics of vivid solar cells, the heed is towards the solar cells through extremely tinny absorber, solar cells by quantum dots absorber coatings. In accordance with which we have discussed about the quantum dot solar cells keeping electrical parameters as the highest priority. Herein we present some small review on recent studies in QD solar cells considering their electrical and impedance properties, effect of incorporation of nano materials in solar cells.
2017
The high surface to volume ratio of lead sulfide quantum dots (PbS QDs) leads to a high density of detrimental trap states caused by lattice imperfections on the QD surface. Introducing a thin shell of a wide bandgap semiconductor to the QD surface is a promising method to passivate these trap states. Here we demonstrate solar cells made from PbS-CdS core-shell QDs, yielding a 147 mV increase in VOC compared to core-only PbS QDs. We explore the physical reason for this enhancement and demonstrate that it is indeed caused by improved passivation of the PbS surface by the CdS shell, leading to a lower electron trap density. Published as: M. J. Speirs, D. M. Balazs, H.-H. Fang, L.-H. Lai, L. Protesescu, M. V. Kovalenko and M. A. Loi, J. Mater. Chem. A 2015, 3, 1450-1457
Advanced Materials, 2011
Colloidal quantum dots (CQDs) are solution-processed semiconductors of interest in low-cost photovoltaics. Tuning of the bandgap of CQD films via the quantum size effect enables customization of solar cells' absorption profile to match the sun's broad visible- and infrared-containing spectrum reaching the earth. Here we review recent progress in the realization of low-cost, efficient solar cells based on CQDs. We focus in particular on CQD materials and approaches that provide both infrared and visible-wavelength solar power conversion CQD photovoltaics now exceed 5% solar power conversion efficiency, achieved by the introduction of a new architecture, the depleted-heterojunction CQD solar cell, that jointly maximizes current, voltage, and fill factor. CQD solar cells have also seen major progress in materials processing for stability, recently achieving extended operating lifetimes in an air ambient. We summarize progress both in device operation and also in gaining new insights into materials properties and processing - including new electrical contact materials and deposition techniques, as well as CQD synthesis, surface treatments, film-forming technologies - that underpin these rapid advances.
Thin Solid Films, 2008
We have demonstrated recently that two below bandgap energy photons can lead to the creation of one electron-hole pair in a quantum-dot intermediate band solar cell (QD-IBSC). To be effective, the devices used in the experiments were designed to a) half-fill the intermediate band with electrons; b) to allocate the quantum dots in a flat-band potential region, and c) to prevent tunnelling from the n emitter into the intermediate band. QD-IBSCs have also shown degradation in their open-circuit voltage when compared with their counterparts without quantum dots. This loss is due to the presence of the intermediate band (IB) together with the incapacity of the quantum dots to absorb sufficient below bandgap light as to contribute significantly to the photogenerated current. It is predicted, nevertheless, that this voltage loss will diminish if concentration light is used leading to devices with efficiency higher than single gap solar cells. A circuit model that includes additional recombination levels to the ones introduced by the IB is described to support this discussion.
Thin Solid Films, 2008
We have demonstrated recently that two below bandgap energy photons can lead to the creation of one electron-hole pair in a quantum-dot intermediate band solar cell (QD-IBSC). To be effective, the devices used in the experiments were designed to a) half-fill the intermediate band with electrons; b) to allocate the quantum dots in a flat-band potential region, and c) to prevent tunnelling from the n emitter into the intermediate band. QD-IBSCs have also shown degradation in their open-circuit voltage when compared with their counterparts without quantum dots. This loss is due to the presence of the intermediate band (IB) together with the incapacity of the quantum dots to absorb sufficient below bandgap light as to contribute significantly to the photogenerated current. It is predicted, nevertheless, that this voltage loss will diminish if concentration light is used leading to devices with efficiency higher than single gap solar cells. A circuit model that includes additional recombination levels to the ones introduced by the IB is described to support this discussion.
Chemical Reviews, 2014
Materials Today, 2012
Nanomaterials form a flexible material platform that has great promise for providing new ways to approach solar energy conversion. The synthesis, investigation, and utilization of these novel nanostructures lie at the interface between chemistry, physics, materials science, and engineering. The chemistry community is providing simple and safe solution phase syntheses that yield monodisperse, passivated nanocrystals (NCs) of high optoelectronic quality with a growing degree of control over composition, shape, and structure. These novel structures provide physicists and materials scientists with new avenues towards controlling energy flow. One of the largest scientific challenges regarding solar energy conversion is increasing the efficiency of the primary photoconversion process. In recent years we have studied the process of multiple exciton generation (MEG), where a photon bearing at least twice the energy of the bandgap can produce two or more electron-hole pairs and thereby bypass some wasteful heat production. 1,2
Pure and Applied Chemistry, 2000
A systematic study on the fabrication of quantum dots sensitized solar cells (QDSSCs) exploiting hybrid networks of semiconducting light harvesters is presented, which shows how the engineering of band gaps of the device components by a very simple technique allows improving the solar energy conversion performances. Panchromatic devices are fabricated and tested, and correspondent functional parameters analyzed in order to highlight both advantages and drawbacks of the most common (CdS, CdSe, PbS) quantum dots applied for light collection in QDSSCs. Judicious engineering of the light harvester layer is demonstrated as a simple and powerful strategy for boosting device performances, through the management of light collection in a rather broad range of solar spectrum and photogenerated charges injection and collection. Brought to you by | Biblioteca della Facolta di Medicina Brescia Authenticated | [email protected] author's copy Download Date | 4/27/14 7:42 PM Recently [11]
MRS Bulletin, 2007
Semiconductor quantum dots may be used in so-called third-generation solar cells that have the potential to greatly increase the photon conversion efficiency via two effects: (1) the production of multiple excitons from a single photon of sufficient energy and (2) the formation of intermediate bands in the bandgap that use sub-bandgap photons to form separable electron–hole pairs. This is possible because quantization of energy levels in quantum dots produces the following effects: enhanced Auger processes and Coulomb coupling between charge carriers; elimination of the requirement to conserve crystal momentum; slowed hot electron–hole pair (exciton) cooling; multiple exciton generation; and formation of minibands (delocalized electronic states) in quantum dot arrays. For exciton multiplication, very high quantum yields of 300–700% for exciton formation in PbSe, PbS, PbTe, and CdSe quantum dots have been reported at photon energies about 4–8 times the HOMO–LUMO transition energy (qu...
Non-conventional sources of energy are widely being practiced because they are the cleanest and the most abundant source of energy that is available in the earth. Effective utilization of available solar energy to produce the electricity is vital for the increase in the growth of deployment of solar power generation. Owing to the high efficiency and its ease of operation the study of Quantum Dot solar cells has been on an increase ever since the onset of this decade. Extensive research work has been carried out to make these cells more feasible and commercially viable. Some of the areas of this extensive work include Sensitized Solar Cells, Multiple Excitation Effect and Carbon Quantum Dot. The different materials and methods used in quantum dot solar cells are discussed in this article.
The intermediate band solar cell concept can be implemented in practice by means of quantum dots (QDs), but a number of challenges must be solved in order to make progress. This paper describes some of them: a) the problem of having the quantum dots embedded in the space charge region, b) the identification of the energy levels involved in the QD system and c) the weak absorption provided by the dots. Regarding the first, the inclusion of semiconductor dumping field layers sandwiching the region containing the stack of QDs is suggested as a way to drive the QDs into a flat band potential region. Concerning "b", the intermediate band is found to be separated from the conduction band by only 0.2 eV, far from the optimum value. Finally, the weak light absorption provided by the dots is discussed as a factor, together with the low intermediate band to conduction band bandgap that prevents a significant quasi-Fermi level split between the IB and the CB under normal illumination conditions.
Nano Letters, 2011
The room temperature photoluminescence (PL) in QDoSCs has been measured under the short circuit conditions to match to the short circuit current measurements. To stimulate the PL we used the 532 nm line from a frequency-doubled neodymium doped yttrium aluminum garnet (Nd:YAG) laser with the 20 μm diameter of the laser spot on a sample. The PL signals from the samples were measured by an InGaAs detector array. The PL spectra were obtained under excitation intensities of 0.3, 0.5, 1, and 4 W/cm 2. PL data for low intensities are presented in the main text. Figure 1 shows the spectral dependence of the PL on the doping level in n-doped samples under intensity of 0.5 W/cm 2 .
2016
One of the more rapidly growing fields in science today is solar energy conversion. An emerging technology in this field is the use of so called ”Quantum Dots”, semiconductors which are small enough to have discrete energy levels. In this literature review, some of the basic photochemisty and photophysics of solar energy generation will be established. A series of articles will then be reviewed, painting a picture of how quantum dots can convert the energy found in photons to useful electricity.
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