http://www.hindawi.comThe latest articles from Hindawi Publishing Corporation© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2009/457549.htmlIn this paper, we propose to adapt the multilinear algebra tools to the tensor of Transmission Cross-Coefficients (TCC) values for aerial image simulation in order to keep the data tensor as a whole entity. This new approach implicitly extends the singular value decomposition (SVD) to tensors, that is, Higher Order SVD or TUCKER3 tensor decomposition which is used to obtain lower rank-(K1, K2, K3, K4) tensor approximation (LRTA (K1, K2, K3, K4)). This model requires an Alternating Least Square (ALS) process known as TUCKALS3 algorithm. The needed number of kernels is estimated using two adapted criteria, well known in signal processing and information theory. For runtime improvement, we use the fixed point algorithm to calculate only the needed eigenvectors. This new approach leads to a fast and accurate algorithm to compute aerial images.Caroline Fossati, Salah Bourennane, Romuald Sabatier, and Antonio Di Giacomo© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2009/967613.htmlWe describe a fast way to encode a gray-scale image with quadratic properties in polymer thin film doped with azo dye. Under a two photon microscopy setup, we induced disorientation in corona-poled azo dye copolymer thin films by a focused near infrared (IR) femtosecond laser beam of variable exposure time. In situ, the sample was then scan to detect the second harmonic signal. We have also tested the backward detection which can provide reading and writing through a single microscope objective. In addition, we were able to store binary 3D information in the bulk of a 50 μm thick film of the same material.E. Sungur, D. Carrara, G. Taupier, A. Fort, L. Mager, A. Barsella, and K. D. Dorkenoo© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2009/278105.htmlThe theoretical model of Yb3+-Er3+-Tm3+-codoped fiber amplifier pumped by 980 nm laser is proposed, and the rate and power propagation equations are numerically solved to analyze the dependences of the gains at 1500 nm and 1600 nm bands on the activator concentrations, fiber length, pump power, and signal wavelength. The numerical results show that our model is in good agreement with experimental result, and with pump power of 200 mW and fiber length varying from 0.15 to 1.5 m, the gains at the two bands may reach 10.0–20.0 dB when the codoping concentrations of Yb3+, Er3+, and Tm3+ are in the ranges 1.0–3.0×1025, 1.0–3.0×1024, and 1.0–3.0×1024 ions/m3, respectively. The fiber parameters may be optimized to flatten the gain spectra.Chun Jiang© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2009/924340.htmlA numerical analysis is presented on the long-haul wavelength-division multiplexing (WDM) transmission system employing fiber-optic parametric amplifier (FOPA) cascades based on one-pump FOPA model with Raman Effect taken into account. The end-to-end equalization scheme is applied to optimize the system features in terms of proper output powers and signal-to-noise ratios (SNRs) in all the channels. The numerical results show that—through adjusting the fiber spans along with the number of FOPAs as well as the channel powers at the terminals in a prescribed way—the transmission distance and system performance can be optimized. By comparing the results generated by different lengths of fiber span, we come to the optimal span length to achieve the best transmission performance. Furthermore, we make a comparison among the long-haul WDM transmission systems employing different inline amplifiers, namely, FOPA, erbium-doped fiber amplifier (EDFA), and Fiber Raman Amplifier (FRA). FOPA demonstrates its advantage over the other two in terms of system features.Xiaohong Jiang and Chun Jiang© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2009/918351.htmlLuminescent ink from europium-doped Y2O3 ( Y2O3:Eu) has been synthesized by two steps method: first, synthesis of luminescent powder of Y2O3:Eu by simple heating of metallic nitrates in a polymer solution and second, dispersing the powder in a polyvinyl alcohol (PVA) solution. The stability of the ink (luminescent colloid) was strongly affected by mixing process of the powder and the solution. Mixing process must be performed for a long time (about 8 hours) at above room temperature to product stable colloids. We observed that mixing at 30–40∘C resulted in a stable and highly dispersed colloid. The writing test was performed on a white paper to show the potential use of the colloid for making security codes. Astuti, Mikrajuddin Abdullah, and Khairurrijal© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/684349.htmlBy combining polymer-dispersed liquid crystal (PDLC) and holography, holographic PDLC (H-PDLC) has emerged as a new composite material for switchable or tunable optical devices. Generally, H-PDLC structures are created in a liquid crystal cell filled with polymer-dispersed liquid crystal materials by recording the interference pattern generated by two or more coherent laser beams which is a fast and single-step fabrication. With a relatively ideal phase separation between liquid crystals and polymers, periodic refractive index profile is formed in the cell and thus light can be diffracted. Under a suitable electric field, the light diffraction behavior disappears due to the index matching between liquid crystals and polymers. H-PDLCs show a fast switching time due to the small size of the liquid crystal droplets. So far, H-PDLCs have been applied in many promising applications in photonics, such as flat panel displays, switchable gratings, switchable lasers, switchable microlenses, and switchable photonic crystals. In this paper, we review the current state-of-the-art of H-PDLCs including the materials used to date, the grating formation dynamics and simulations, the optimization of electro-optical properties, the photonic applications, and the issues existed in H-PDLCs.Y. J. Liu and X. W. Sun© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/373259.htmlOptical intensity modulation has been demonstrated through switching the optical beam between the main core waveguide and a closely attached leaky slab waveguide by applying a low-voltage electrical field. Theory for simulating such an LiNbO3 slab-coupled waveguide structure was suggested, and the result indicates the possibility of making the spatial guiding mode large, circular and symmetric, which further allows the potential to significantly reduce the coupling losses with adjacent lasers and optical networks. Optical intensity modulation using electro-optic effect was experimentally demonstrated in a 5 cm long waveguide fabricated by using a procedure of soft proton exchange and then an overgrowth of thin LN film on top of a c-cut LiNbO3 wafer.Yalin Lu and Kitt Reinhardt© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/532351.htmlPolycrystalline silicon thin-film solar cells on glass obtained by solid-phase crystallization (SPC) of PECVD-deposited a-Si precursor diodes are capable of producing large-area devices with respectable photovoltaic efficiency. This has not yet been shown for equivalent devices made from evaporated Si precursor diodes (“EVA” solar cells). We demonstrate that there are two main problems for the metallization of EVA solar cells: (i) shunting of the p-n junction when the air-side metal contact is deposited; (ii) formation of the glass-side contact with low contact resistance and without shunting. We present a working metallization scheme and first current-voltage and quantum efficiency results of 2 cm2 EVA solar cells. The best planar EVA solar cells produced so far achieved fill factors up to 64%, series resistance values in the range of 4-5 Ωcm2, short-circuit current densities of up to 15.6 mA/cm2, and efficiencies of up to 4.25%. Using numerical device simulation, a diffusion length of about 4 μm is demonstrated for such devices. These promising results confirm that the device fabrication scheme presented in this paper is well suited for the metallization of EVA solar cells and that the electronic properties of evaporated SPC poly-Si materials are sufficient for PV applications.O. Kunz, Z. Ouyang, J. Wong, and A. G. Aberle© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/467145.htmlYalin Lu, Hiroshi Murata, and Chang-Qing Xu© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/587091.htmlThe detection of an optical signal modulated at 15 GHz was demonstrated experimentally by using difference frequency generation based on a second-order nonlinear optical effect in a periodically poled LiTaO3 microwave rectangular waveguide. The measured frequency dependence of the generated microwave signal was in good agreement with the theoretically expected result. An interesting application of the proposed device is the detection of high-speed optical clock detection.Hiroshi Murata and Yasuyuki Okamura© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/654280.htmlOptical waveguides were fabricated on z-cut stoichiometric LiTaO3 (SLT) by using the proton-exchange method. The surface index change for the extraordinary ray on the SLT substrate resulting from the proton exchange was 0.017, which coincided well with congruent LiTaO3 substrates. The proton exchange coefficient in the SLT was 0.25×10−12 cm2/s. The application of the SLT waveguide to a quasi-velocity-matched travelling-wave electrooptic modulator with periodically polarization-reversed structure is also reported.Hiroshi Murata and Yasuyuki Okamura© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/752847.htmlWe estimate the phase velocity of a modulation microwave in a quasi-velocity-matched (QVM) electro-optic (EO) phase modulator (QVM-EOM) using EO sampling which is accurate and the most reliable technique for measuring voltage waveforms at an electrode. The substrate of the measured QVM-EOM is a stoichiometric periodically domain-inverted LiTaO3 crystal. The electric field of a standing wave in a resonant microstrip line (width: 0.5 mm, height: 0.5 mm) is measured by employing a CdTe crystal as an EO sensor. The wavelength of the traveling microwave at 16.0801 GHz is determined as 3.33 mm by fitting the theoretical curve to the measured electric field distribution. The phase velocity is estimated as vm=5.35×107 m/s, though there exists about 5% systematic error due to the perturbation by the EO sensor. Relative dielectric constant of εr=41.5 is led as the maximum likelihood value that derives the estimated phase velocity.Shintaro Hisatake, Akira Kaino, Tomoaki Yasuda, and Tadao Nagatsuma© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/421054.htmlMgO:LiNbO3 is an attractive nonlinear-optic crystal for quasiphasematched (QPM) nonlinear-optic devices. This paper reports a new formation method of domain-inverted gratings for QPM in MgO:LiNbO3. Domain inversion of MgO:LiNbO3 by voltage application under UV light was characterized, and reduction of the voltage required for inversion was demonstrated. Results of voltage application under periodic UV light suggested that suppression of excess lateral expansion of the domain inverted regions on −Z surface was crucial for domain-inverted grating formation. Voltage application to a crystal with a photoconductive cladding layer under periodic UV light was proposed. The cladding layer suppressed the expansion, and the domain-inverted gratings with period of 18 μm and area of 25×5  mm2 were obtained. The formation method does not require the photolithography process and allows the formation by voltage application at room temperature, and therefore, is quite simple and productive.Masatoshi Fujimura and Toshiaki Suhara© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/428971.htmlNoise characteristics of second-harmonic generation (SHG) in periodically poled lithium niobate (PPLN) using the quasiphase matching (QPM) technique are analyzed experimentally. In the experiment, a0.78 μm second-harmonic (SH) wave was generated when a 1.56 μm fundamental wave passed through a PPLN crystal (bulk or waveguide). The time-domain and frequency-domain noise characteristics of the fundamental and SH waves were analyzed. By using the pump-probe method, the noise characteristics of SHG were further analyzed when a visible light (532 nm) and an infrared light (1090 nm) copropagated with the fundamental light, respectively. The noise characterizations were also investigated at different temperatures. It is found that for the bulk and waveguide PPLN crystals, the SH wave has a higher relative noise level than the corresponding fundamental wave. For the same fundamental wave, the SH wave has lower noise in a bulk crystal than in a waveguide, and in MgO-doped PPLN than in undoped PPLN. The 532 nm irradiation can lead to higher noise in PPLN than the 1090 nm irradiation. In addition, increasing temperature of device can alleviate the problem of noise in conjunction with the photorefractive effect incurred by the irradiation light. This is more significant in undoped PPLN than in MgO-doped one.Yong Wang, Jorge Fonseca-Campos, Wan-guo Liang, Chang-Qing Xu, and Ignacio Vargas-Baca© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/151487.html908 mW of green light at 532 nm were generated by intracavity quasiphase matching in a bulk periodically poled MgO:LiNbO3 (PPMgLN) crystal. A maximum optical-to-optical conversion efficiency of 33.5% was obtained from a 0.5 mm thick, 10 mm long, and 5 mol% MgO:LiNbO3 crystal with an end-pump power of 2.7 W at 808 nm. The temperature bandwidth between the intracavity and single-pass frequency doubling was found to be different for the PPMgLN. Reliability and stability of the green laser were evaluated. It was found that for continuous operation of 100 hours, the output stability was better than 97.5% and no optical damage was observed.Shaowei Chu, Ying Zhang, Bin Wang, and Yong Bi© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/956908.htmlWe have experimentally demonstrated an efficient all-fiber passively Q-switched Yb-doped fiber laser with Samarium doped fiber as a saturable absorber. Average output power of 3.4 W at a repetition rate of 250 kHz and a pulse width of 1.1 microseconds was obtained at a pump power of 9.0 W. By using this fiber laser system and an MgO-doped congruent periodically poled lithium niobate (MgO:c-PPLN), second harmonic generation (SHG) output at 532 nm was achieved at room temperature. The conversion efficiency is around 4.2% which agrees well with the theoretical simulation.Yi Gan, Xijia Gu, Joyce Y. C. Koo, Wanguo Liang, and Chang-qing Xu© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/948614.htmlAn oxide-based multilayer structure was proposed to realize negative refraction. The multilayer composes of alternative layers having negative permittivity and negative permeability, respectively. In order to realize negative refraction, their dielectric and magnetic resonances of layers will be tuned to the frequency as close as possibly via changing their temperature, composition, structure, and so forth. Such oxide-based NIMs are attractive for their potential applications as optical super lenses, imagers, optical cloaking, sensors, and so forth, those are required with low-loss, low-cost, and good fabrication flexibility.Yalin Lu, Gail J. Brown, and Kitt Reinhardt© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/208458.htmlNonlinear frequency conversion remains one of the dominant approaches to efficiently generate THz waves. Significant material absorption in the THz range is the main factor impeding the progress towards this direction. In this research, a new multicladding nonlinear fiber design was proposed to solve this problem, and as the major experimental effort, periodic domain structure was introduced into lithium niobate single-crystal fibers by electrical poling. The introduced periodic domain structures were nondestructively revealed using a crossly polarized optical microscope and a confocal scanning optical microscope for quality assurance.Yalin Lu and Kitt Reinhardt© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/948294.htmlWe discuss a new method to design traveling-wave electrooptic modulators with controlled frequency responses using nonperiodically polarization-reversed structure. Using our method, the frequency responses of both magnitude and phase of modulation index are controllable. Several electrooptic modulators for advanced modulation formats such as duobinary modulation and wideband single-sideband modulation are proposed.Ha Viet Pham, Hiroshi Murata, and Yasuyuki Okamura© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/759340.htmlOne main efficiency loss in industrial solar cells is the shading of the cell caused by the metal front side contacts. With the aerosol-printing technique plus an additional light-induced plating (LIP) step, not only is the geometrical contact width narrowed compared to screen-printed contacts but also the shape of the finger changes. In this work, the effective shading of different finger types is analysed with two different measurement methods. The essential parameter for characterising the finger is the effective width which can be reduced drastically compared to the geometrical width due to total internal reflection at the glass-air layer and the reflection from the roundish edges of the contact fingers into the cell. This parameter was determined with different methods. It could be shown that for aerosol-printed fingers the effective (optical) width is only 38% of its geometrical width, while for standard screen-printed fingers it is 47%. The measured values are compared to a theoretical model for an aerosol-printed and plated finger and are in good agreement.R. Woehl, M. Hörteis, and S. W. Glunz© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/485467.htmlA novel plasma-enhanced chemical vapour deposited (PECVD) stack layer system consisting of a-SiOx:H, a-SiNx:H, and a-SiOx:H is presented for silicon solar cell rear side passivation. Surface recombination velocities below 60 cm/s (after firing) and below 30 cm/s (after forming gas anneal) were achieved. Solar cell precursors without front and rear metallisation showed implied open-circuit voltages Voc values extracted from quasi-steady-state photoconductance (QSSPC) measurements above 680 mV. Fully finished solar cells with up to 20.0% energy conversion efficiency are presented. A fit of the cell's internal quantum efficiency using software tool PC1D and a comparison to a full-area aluminium-back surface field (Al-BSF) and thermal SiO2 is shown. PECVD-ONO was found to be clearly superior to Al-BSF. A separation of recombination at the metallised and the passivated area at the solar cell's rear is presented using the equations of Fischer and Kray. Nuclear reaction analysis (NRA) has been used to evaluate the hydrogen depth profile of the passivation layer system at different stages.M. Hofmann, S. Kambor, C. Schmidt, D. Grambole, J. Rentsch, S. W. Glunz, and R. Preu© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2007/024521.abs.htmlIn 2006, around 86% of all wafer-based silicon solar cells were produced using screen printing to form the silver front and aluminium rear contacts and chemical vapour deposition to grow silicon nitride as the antireflection coating onto the front surface. This paper reviews this dominant solar cell technology looking into state-of-the-art equipment and corresponding processes for each process step. The main efficiency losses of this type of solar cell are analyzed to demonstrate the future efficiency potential of this technology. In research and development, more various advanced solar cell concepts have demonstrated higher efficiencies. The question which arises is “why are new solar cell concepts not transferred into industrial production more frequently?”. We look into the requirements a new solar cell technology has to fulfill to have an advantage over the current approach. Finally, we give an overview of high-efficiency concepts which have already been transferred into industrial production.Dirk-Holger Neuhaus and Adolf Münzer© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2007/060319.abs.htmlArmin Aberle© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/781524.htmlWe study the frequency spectrum of nanoemitters placed in a microsphere with a quasiperiodic subwavelength spherical stack. The spectral evolution of transmittancy at the change of thickness of two-layer blocks, constructed following the Fibonacci sequence, is investigated. When the number of layers (Fibonacci order) increases, the structure of spectrum acquires a fractal form. Our calculations show the radiation confinement and gigantic field enhancement, when the ratio of layers’ widths in twolayer blocks of the stack is close to the golden mean value.Gennadiy N. Burlak and A. Diaz-de-Anda© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2008/739135.htmlWe describe a simple configuration in which the extraordinary optical transmission effect through subwavelength hole arrays in noble-metal films can be switched by the semiconductor-to-metal transition in an underlying thin film of vanadium dioxide. In these experiments, the transition is brought about by thermal heating of the bilayer film. The surprising reverse hysteretic behavior of the transmission through the subwavelength holes in the vanadium oxide suggest that this modulation is accomplished by a dielectric-matching condition rather than plasmon coupling through the bilayer film. The results of this switching, including the wavelength dependence, are qualitatively reproduced by a transfer matrix model. The prospects for effecting a similar modulation on a much faster time scale by using ultrafast laser pulses to trigger the semiconductor-to-metal transition are also discussed.E. U. Donev, J. Y. Suh, R. Lopez, L. C. Feldman, and R. F. Haglund Jr.© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2007/018619.abs.htmlThe low-cost chemical bath deposition (CBD) technique is used to prepare CBD-ZnS films as antireflective (AR) coating for multicrystalline silicon solar cells. The uniformity of CBD-ZnS film on large area of textured multicrystalline silicon surface is the major challenge of CBD technique. In the present work, attempts have been made for the first time to improve the rate of deposition and uniformity of deposited film by controlling film stoichiometry and refractive index and also to minimize reflection loss by proper optimization of molar percentage of different chemical constituents and deposition conditions. Reasonable values of film deposition rate (12.13 Å′/min.), good film uniformity (standard deviation <1), and refractive index (2.35) along with a low percentage of average reflection (6-7%) on a textured mc-Si surface are achieved with proper optimization of ZnS bath. 12.24% efficiency on large area (125 mm × 125 mm) multicrystalline silicon solar cells with CBD-ZnS antireflection coating has been successfully fabricated. The viability of low-cost CBD-ZnS antireflection coating on large area multicrystalline silicon solar cell in the industrial production level is emphasized.U. Gangopadhyay, K. Kim, S. K. Dhungel, H. Saha, and J. Yi© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2007/040285.abs.htmlSolar cells based on organic semiconductors have attracted much attention. The thickness of the active layer of organic solar cells is typically only 100 nm thin, which is about 1000 times thinner than for crystalline silicon solar cells and still 10 times thinner than for current inorganic thin film cells. The low material consumption per area and the easy processing of organic semiconductors offer a huge potential for low cost large area solar cells. However, to compete with inorganic solar cells the efficiency of organic solar cells has to be improved by a factor of 2-3. Several organic semiconducting materials have been investigated so far, but the optimum material still has to be designed. Similar as for organic light emitting devices (OLED) small molecules are competing with polymers to become the material of choice. After a general introduction into the device structures and operational principles of organic solar cells the three different basic types (all polymer based, all small molecules based and small molecules mixed with polymers) are described in detail in this review. For each kind the current state of research is described and the best of class reported efficiencies are listed.Thomas Kietzke© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2007/083657.abs.htmlThe changes in open-circuit voltage (Voc), short-circuit current density (Jsc), and internal quantum efficiency (IQE) of aLuminum induced crystallization, ion-assisted deposition (ALICIA) polycrystalline silicon thin-film solar cells on low-temperature glass substrates due to rapid thermal anneal (RTA) treatment and subsequent remote microwave hydrogen plasma passivation (hydrogenation) are examined. Voc improvements from 130 mV to 430 mV, Jsc improvements from 1.2 mA/cm2 to 11.3 mA/cm2, and peak IQE improvements from 16% to > 70% are achieved. A 1-second RTA plateau at 1000°C followed by hydrogenation increases the Jsc by a factor of 5.5. Secondary ion mass spectroscopy measurements are used to determine the concentration profiles of dopants, impurities, and hydrogen. Computer modeling based on simulations of the measured IQE data reveals that the minority carrier lifetime in the absorber region increases by 3 orders of magnitude to about 1 nanosecond (corresponding to a diffusion length of at least 1 μm) due to RTA and subsequent hydrogenation. The evaluation of the changes in the quantum efficiency and Voc due to RTA and hydrogenation with computer modeling significantly improves the understanding of the limiting factors to cell performance.Mason L. Terry, Daniel Inns, and Armin G. Aberle© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2007/046861.abs.htmlWe study the properties of various anisotropic left-handed slab waveguides. The analysis is extended to anisotropic μ-negative slab waveguides. The possible existence of the plasmon modes in various anisotropic slab waveguide configurations is discussed. An FDTD program is developed to investigate the potential device applications of these anisotropic structures. A new signal detector and a two-channel harmonic separator multiplexer are designed employing the μ-negative slab waveguide.Hamidreza Salehi, Sujeet K. Chaudhuri, and Raafat R. Mansour© 2010, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aoe/2007/036970.abs.htmlWe review the field of thin-film silicon solar cells with an active layer thickness of a few micrometers. These technologies can potentially lead to low cost through lower material costs than conventional modules, but do not suffer from some critical drawbacks of other thin-film technologies, such as limited supply of basic materials or toxicity of the components. Amorphous Si technology is the oldest and best established thin-film silicon technology. Amorphous silicon is deposited at low temperature with plasma-enhanced chemical vapor deposition (PECVD). In spite of the fundamental limitation of this material due to its disorder and metastability, the technology is now gaining industrial momentum thanks to the entry of equipment manufacturers with experience with large-area PECVD. Microcrystalline Si (also called nanocrystalline Si) is a material with crystallites in the nanometer range in an amorphous matrix, and which contains less defects than amorphous silicon. Its lower bandgap makes it particularly appropriate as active material for the bottom cell in tandem and triple junction devices. The combination of an amorphous silicon top cell and a microcrystalline bottom cell has yielded promising results, but much work is needed to implement it on large-area and to limit light-induced degradation. Finally thin-film polysilicon solar cells, with grain size in the micrometer range, has recently emerged as an alternative photovoltaic technology. The layers have a grain size ranging from 1 μm to several tens of microns, and are formed at a temperature ranging from 600 to more than 1000∘C. Solid Phase Crystallization has yielded the best results so far but there has recently been fast progress with seed layer approaches, particularly those using the aluminum-induced crystallization technique.Guy Beaucarne© 2010, Hindawi Publishing Corporation. All rights reserved.