Solar ultrathin

Another area of development is in lower-cost thin- and ultrathin-film designs. One such product is made by Nanosolar of copper indium gallium selenide (CIGS), which is claimed to achieve up to 19.5% efficiency and is as thin as a newspaper. This claim is yet to be proved. The collector cost is also reduced, because the substrate material on which the ink is printed is much less expensive than the stainless steel substrates that are often used in thin-film solar panels. The manufacturer claims a five- to tenfold reduction in the collector cost (about 1/W) compared to conventional PV cells. 

Larger installations could also use solar laminates and solar shingles. Such projects already exist. For example, GM has a 1 mW solar installation in Rancho Cucamonga, California. Many other such systems have been installed, and new designs, such as the ultrathin (Nanosolar) shingles, are under development, and promise drastic reductions in costs. 

We know that production volume and the associated mass production do affect costs. For example, during the last decade, the cost of solar collector cells (PVs) halved, and the production cost of solar electricity dropped to about 12c /kWh. If the claims of Nanosolar (an ultrathin-film solar collector manufacturer) turn out to be correct, collector costs might drop drastically. With a reduction in solar collector costs, the cost of solar-hydrogen has also been dropping. Today, the cost projections for large-capacity LH2 plants are around 3 to 5 per kg. 

Past experience shows that as the equipment needed for new technologies starts to be mass produced, its prices drop. The cost of wind power-generated electricity has already been reduced to one quarter of that of the first installations. An ultrathin-film solar collector manufacturer (Nanosolar) claims that it will soon market collectors at costs that are severalfold less expensive than today s PV prices. We do not know if that particular claim is correct or not, but we know that time is on our side. Therefore, it is realistic to expect that as markets expand, the costs of mass-produced renewable energy devices will also drop and the cost of transition to a solar-hydrogen economy over several decades will become not only affordable, but will also create jobs and an economic boom. We should remember that drastic changes can occur rapidly after all, a century ago electricity was a luxury that only 3% of the households had. The same will occur with renewable energy over the 21st century. 

The fuel used to make solar-hydrogen is free (sunshine) and unlimited, the raw material for H2 is water, and the emission when burning the H2 in fuel cells, internal combustion engines, or in power plants is distilled water. The cost of building the solar-hydrogen plants will be known once the demonstration power plant described in this book is built. It might turn out that this cost is already competitive but whatever it is, we know that it will drop by an order of magnitude when the mass production of ultrathin-film solar collectors and reversible fuel cells is started. 

The cathode photocurrent is in proportion to the number of TCPP layers at least up to 10 cycles. The efficiency is greatly dependent on the kinds of oxide gel. These experimental observations suggest that electron transfer from the electrode to the porphyrin via the oxide gel layer is an essential mechanism of the photocurrent generation. Oxygen molecules as an electron acceptor readily diffuse in the oxide gel films of about 20 nm thickness. The electron transfer from the electrode to the porphyrin is assisted by satisfactory conductivity of the gel layer. The overall photocurrent value is considerably smaller than the conventional wet solar cell [11]. However, modification of the electrode surface by ultrathin oxide gel films will facilitate the design of novel light harvesting devices. 

At their present state of development, ETA cells typically exhibit open-circuit voltages of 0.6-0.7 V and photocurrents of 5-15 mA cm . While the fill factors in the earlier ETA cells were often poor, typically -20%, more recent cells have improved fill factors, typically -60%. Overall, the solar conversion efficiencies are modest, as shown in Fig. 1.2 to date ri p values of approximately 5% have been obtained (Nanu et al., 2005). Insertion of an ultrathin mnnel barrier layer of an insulator such as AI2O3 or MgO can improve the open-circuit voltage (Wienke et al., 2003). Incorporation of quantum... 

Apart from serving as substrate and conductive layer, polymers can be also used as functional layers in the fabrication of PSCs. An ultrathin and lightweight polymer-based solar cell with a thickness of less than 2 pm had been developed on a 1.4 pm-thick PET substrate (Fig. 9.1F). The resulting PSC showed a comparable power conversion efficiency of 4.2% with high flexibility. By adhering the flexible PSC to a prestretched elastomer, a stretchable PSC can be also fabricated. Even during repeated compression and stretching, these stretchable PSCs showed stable photovoltaic performances (Kaltenbrurmer etal., 2012). 

Kaltenbrurmer, M., White, M.S., Glowacki, E.D., Sekitani, T., Someya, X, Sariciftci, N.S., Bauer, S., 2012. Ultrathin and lightweight organic solar cells with high flexibility. Nat. Commun. 3,770. 

The manifestation of discontinuity in the IR spectra of an ultrathin film can be predicted within the framework of the EMT, treating the film as an effective medium consisting of particles and air. Many EMT studies (see, e.g.. Ref. [346]) have been devoted to metal films because of their applications in solar energy conversion and surface enhancement spectroscopies (see below) and as radiation filters. Some results for ultrathin metallic films will be discussed below. In principle, these should apply to ionic crystal clusters in the spectral range where n < k as well as metallic clusters, because there is no physical difference in the interpretation of absorption spectra of metallic and ionic crystal clusters. 

ULTRATHIN OXIDE LAYERS IN SILICON SCHOTTKY-TYPE SOLAR CELLS... 

Besides the standard methods of SIMS, AES, and XPS for investigation of these ultrathin dielectric layers in Schottky-type solar cells, IRRAS has also been applied [5-8]. Ultrathin (2-10-nm) Si02 films in metal-oxide-silicon strnctnres have also been investigated by IRRAS [9-14]. 

Electrochemically generated ultrathin films on semiconductors have been studied intensively in recent years in the context of flotation, electrocatalysis, solar energy storage, microelectronics, photocatalytic reactions, photodegradation of organics. 

Transparent conducting thin films are used in numerous applications such as solar cells, displays, commxmication devices, LED, etc. Highly conductive SWCNT films show transmittance comparable or higher than the commercial indium-tin-oxide (ITO) used to fabricate transparent conducting films. Wu et al. have used ultrathin transparent conducting films of CNTs as optical coupling in photonic devices to fabricate an electric field-activated optical modulator [181]. 

YOO 08] Yoon J., Baca A.J., Park S.l. et al, Ultrathin sihcon solar microcells for semitransparent, mechanically flexible and microconcentrator module designs , Nature Materials, vol. 7, pp. 907-915, 2008. 

Wei G, Lunt RR, Sun K, Wang S, Thompson ME, Forrest SR (2010) Efficient, ordered bulk heterojunction nanocrystalline solar cells by annealing of ultrathin squaraine thin films. Nano Lett 10 3555... 

Klahr, B. M. Martinson, A. B. F. Hamann, T. W., Photoelectrochemical investigation of ultrathin film iron oxide solar cells prepared by atomic layer deposition. Langmuir mW, 27, 461-468. 

Y. W. Chen, Z. H. Hu, Z. M. Zhong, W. Shi, J. B. Peng, J. Wang and Y. Cao, Aqueous Solution Processed, Ultrathin ZnO Film with Low Conversion Temperature as the Electron Transport Layer in the Inverted Polymer Solar Cells,/. Phys. Chem. C, 2014,118, 21819-21825. 

The first organic tandem solar cell was published in 1990 by Hiramoto et al, who employed two identical subcells composed of bilayers of a metal-free phthalocyanine and a perylene tetracarboxylic derivative with an ultrathin Au layer to interconnect the two subcells to achieve an almost doubling of the voltage. More than a decade later, in 2002, Forrest et reported on two, three, and five stacked heterojunction cells consisting of copper phthalocyanine (CuPc) as a donor and perylenetetracarboxylic bis-benzimidazole (PCTBI) as an acceptor. Ultrathin ( 5 A) layers of Ag clusters were placed between the heterojunctions to interconnect the subcells. Similar results were described by Tsutsui et In 2004, Leo and Pfeifer et intro-... 

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