Plasmonic nanostructures have been recently investigated as a possible way to improve absorption of light in solar cells. The strong interaction of small metal nanostructures with light allows ...control over the propagation of light at the nanoscale and thus the design of ultrathin solar cells in which light is trapped in the active layer and efficiently absorbed. In this paper we review some of our recent work in the field of plasmonics for improved solar cells. We have investigated two possible ways of integrating metal nanoparticles in a solar cell. First, a layer of Ag nanoparticles that improves the standard antireflection coating used for crystalline and amorphous silicon solar cells has been designed and fabricated. Second, regular and random arrays of metal nanostructures have been designed to couple light in waveguide modes of thin semiconductor layers. Using a large-scale, relative inexpensive nano-imprint technique, we have designed a back-contact light trapping surface for a-Si:H solar cells which show enhanced efficiency over standard randomly textured cells.
The paper describes the way to transfer process technology of state-of-the-art high efficiency thin film silicon solar cells fabrication on cheap plastic (such as PET or PEN) substrates, by two ...completely different approaches: (i) by transfer process (Helianthos concept) of thin film silicon cells deposited at high substrate temperature,
T
s (∼200
°C) and (ii) direct deposition on temperature sensitive substrates at low
T
s (∼100
°C). Adaptation of the process parameters and cell processing to the requirement of the flexible/plastic substrate is the most crucial step. In-situ diagnosis of the plasma has been done to understand the effect of inter-electrode distance, substrate temperature and hydrogen dilution on the gas phase conditions. Whereas, for the transfer process, the inter-electrode distance is a critical deposition condition that needs to be adapted for the flexible substrates, the direct deposition on plastic substrates has an added issue of loss in material quality and the deposition rate due to depositions at low
T
s. Our studies indicate that ion energy is crucial for obtaining compact films at low temperature and high hydrogen dilution helps to compensate the loss of ion energy at low substrate temperatures. Efficiencies of ∼5.9% and 6.2% have been obtained for n–i–p type a-Si cells on PET and PEN substrates, respectively, using direct deposition. Using an adapted inter-electrode distance, an a-Si/nc-Si tandem cell on plastic (polyester) substrate with an efficiency of 8.1% has been made by Helianthos cell transfer process.
The consequences of implementing a Hot Wire Chemical Vapor Deposition (HWCVD) chamber into an existing in-line or roll-to-roll reactor are described. The hardware and operation of the HWCVD ...production reactor is compared to that of existing roll-to-roll reactors based on Plasma Enhanced Chemical Vapor Deposition. The most important consequences are the technical consequences and the economic consequences, which are both discussed. The technical consequences are adaptations needed to the hardware and to the processing sequences due to the different interaction of the HWCVD process with the substrate and already deposited layers. The economic consequences are the reduced investments in radio frequency (RF) supplies and RF components. This is partially offset by investments that have to be made in higher capacity pumping systems. The most mature applications of HWCVD are moisture barrier coatings for thin film flexible devices such as Organic Light Emitting Diodes and Organic Photovoltaics, and passivation layers for multicrystalline Si solar cells, high mobility field effect transistors, and silicon heterojunction cells (also known as heterojunction cells with intrinsic thin film layers). Another example is the use of Si in thin film photovoltaics. The cost perspective per unit of thin film photovoltaic product using HWCVD is estimated at 0.07€/Wp for the Si thin film component.
•Review of consequences of implementing Hot Wire CVD into a manufacturing plant•Aspects of scaling up to large area and continuous manufacturing are discussed•Economic advantage of introducing a HWCVD process in a production system is estimated•Using HWCVD, the cost for the Si layers in photovoltaic products is 0.08€/Wp.
The leader of todays solar energy revolution is undoubtedly the silicon photovoltaic (PV) module. However, despite the immense progress in efficiency and the phenomenal drop of manufacturing and ...installation costs the dark blue flat panels have not found widespread use in the modern urban environment. The scarcity of available rooftop space, the high cost of land and the irregular metropolitan skyline have not allowed conventional solar technologies to supply cities with clean energy. Thus, new concepts are being investigated to integrate solar generators into new and existing buildings in the form of facades or windows. Luminescent Solar Concentrators (LSCs) offer a novel approach for the utilization of solar irradiation in the form of transparent glazing systems that have the potential to become functional elements of the building envelope. This paper highlights and compares the most recent technological advances in the field of LSC technology and the contribution of colloidal chemistry with reabsorption-free emitters offering broadband absorption and enhanced stability. Combined with a critical study of the newly emerged LSC applications in various fields this study will also attempt to give a possible glimpse of the near future of transparent solar harvesting devices.
Display omitted
•State-of-the-art review in LSCs based on nanoparticles.•Reabsorption in LSCs can be minimized.•Applications in large scale LSCs are presented.
Enhancing solar cell efficiency by using spectral converters van Sark, W.G.J.H.M.; Meijerink, A.; Schropp, R.E.I. ...
Solar energy materials & solar cells/Solar energy materials and solar cells,
05/2005, Letnik:
87, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Planar converters containing quantum dots as wavelength-shifting moieties on top of a multi-crystalline silicon and an amorphous silicon solar cell were studied. The highly efficient quantum dots are ...to shift the wavelengths where the spectral response of the solar cell is low to wavelengths where the spectral response is high, in order to improve the conversion efficiency of the solar cell. It was calculated that quantum dots with an emission at 603
nm increase the multi-crystalline solar cell short-circuit current by nearly 10%. Simulation results for planar converters on hydrogenated amorphous silicon solar cells show no beneficial effects, due to the high spectral response at low wavelength.
Measured and modelled
JV characteristics of crystalline silicon cells below one sun intensity have been investigated. First, the
JV characteristics were measured between 3 and 1000
W/m
2 at 6 light ...levels for 41 industrially produced mono- and multi-crystalline cells from 8 manufacturers, and at 29 intensity levels for a single multi-crystalline silicon between 0.01 and 1000
W/m
2. Based on this experimental data, the accuracy of the following four modelling approaches was evaluated: (1) empirical fill factor expressions, (2) a purely empirical function, (3) the one-diode model and (4) the two-diode model. Results show that the fill factor expressions and the empirical function fail at low light intensities, but a new empirical equation that gives accurate fits could be derived. The accuracy of both diode models are very high. However, the accuracy depends considerably on the used diode model parameter sets. While comparing different methods to determine diode model parameter sets, the two-diode model is found to be preferred in principle: particularly its capability in accurately modelling
V
OC
and efficiency with one and the same parameter set makes the two-diode model superior. The simulated energy yields of the 41 commercial cells as a function of irradiance intensity suggest unbiased shunt resistances larger than about 10
kΩ
cm
2 may help to avoid low energy yields of cells used under predominantly low light intensities. Such cells with diode currents not larger than about 10
−9
A/cm
2 are excellent candidates for Product Integrated PV (PIPV) appliances.
Tungsten- and titanium-doped indium oxide (IWO and ITiO) films were deposited at room temperature by radio frequency (RF) magnetron sputtering, and vacuum post-annealing was used to improve the ...electron mobility. With increasing deposition power, the as deposited films showed an increasingly crystalline nature. Compared with ITiO films, IWO films showed crystallinity at lower RF power. IWO films are partially crystallized at 10
W deposition power and become nearly fully crystalline at 20
W. ITiO films are fully crystalline only at 75
W. For this reason, film thickness has a greater impact on the electrical properties of IWO films than ITiO films. Vacuum post-annealing is more effective in improving electron mobility for amorphous than for (partially) crystalline IWO and ITiO films. Changes in the electrical properties of ITiO films can be better controlled as a function of annealing temperature than those of IWO films. Finally, post annealed 308
nm-thick IWO and 325
nm-thick ITiO films have approximately 80% transmittance in visible and near infrared wavelengths (up to 1100
nm), while their sheet resistances decrease to 9.3 and 10
Ω/□, and their electron mobilities are 51
cm
2V
−
1
s
−
1
and 50
cm
2V
−
1
s
−
1
, respectively, making them suitable for use as Transparent Conductive Oxide layers of low bandgap solar cells.
Microcrystalline silicon oxide (µc-SiOx:H) alloys prepared by plasma enhanced chemical vapor deposition (PECVD) represent a versatile material class for opto-electronic applications especially for ...thin-film and wafer based silicon solar cells. The material is a phase mixture of microcrystalline silicon (µc-Si:H) and amorphous silicon oxide (a-SiOx:H). The possibility to enhance the optical band gap energy and to adjust the refractive index over a considerable range, together with the possibility to dope the material p-type as well as n-type, makes μc-SiOx:H an ideal material for the application as window layer, as intermediate reflector (IR), and as back reflector in thin-film silicon solar cells. Analogously, μc-SiOx:H is a suitable material for p- and n-type contact layers in silicon hetero junction (SHJ) solar cells. The present paper gives an overview on the range of physical parameters (refractive index, optical band gap, conductivity) which can be covered by this material by variation of the deposition conditions. The paper focuses on the interdependence between these material properties and optical improvements for amorphous silicon/microcrystalline silicon (a-Si:H/µc-Si:H) tandem solar cells prepared on different substrates, such as Asahi (VU) and sputtered ZnO:Al. It gives a guideline on possible optical gains when using doped µc-SiOx:H in silicon based solar cells. As intermediate reflector in a-Si:H/µc-Si:H tandem cells µc-SiOx:H leads to an effective transfer of short circuit current generation from the bottom cell to the top cell resulting in a possible thickness reduction of the top cell by 40%. Within another series of solar cells shown in this paper a short circuit current density of 14.1mA/cm² for an a-Si:H/µc-Si:H tandem solar cell with a µc-SiOx:H intermediate reflector is demonstrated. A SHJ solar cell on a flat (non-textured) wafer using p- and n-type doped µc-SiOx:H contact layers with an effective area efficiency of 19.0% is also presented.
•Refractive index of doped µc-SiOx:H can be adjusted over a considerable range.•Doped µc-SiOx:H has a high band gap and appropriate electrical properties.•Application to single junction, tandem and hetero junction solar cells was shown.•Benefits for tandem solar modules and their preparation were demonstrated.•Jsc=14.1mA/cm² for tandem and an η=19.0% for SHJ solar cells were achieved.
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