Film Crystalline Silicon Solar Cells Research Articles

Simulation of multi-layer antireflection film for crystalline silicon solar cell

Based on the design theory of single-layer, double-layer and multi-layer antireflection films, the thickness and refractive index of each layer of three-layer antireflection films are designed and calculated. The theoretical results of double-layer and three-layer antireflection films was simulated by PC1D, and reflectance, internal and external quantum efficiency and device characteristics of solar cells with double-layer and three-layer antireflection coatings were comparative studied. The results show that the three-layer antireflection film has a wider wavelength response range and higher external quantum efficiency, and the conversion efficiency of the three-layer antireflection film Crystalline silicon solar cells is improved by 0.2% compared with the double-layer antireflection film Crystalline silicon solar cells.

Optical absorption theoretical analysis for thin film crystalline silicon solar cells fabricated on the hexagonal close‐packed dome arrays

In this work, the low aspect ratio hexagonal close-packed dome arrays were designed to trap light for c-Si thin film solar cells. The optical performance of the designed solar cell was theoretically studied via simulation based on the rigorous coupled wave analysis in detail. The result of the simulation showed the model of the solar cell with arrays exhibited absorptivity enhancement in the longer wavelength range. Simultaneously, the integral for the AM 1.5 absorbance spectrum of each model showed that the absorption gains reach up to the highest point of 45.13% in the periodicity of 0.7 μm.

Absorption enhancement in thin film solar cells with bilayer silver nanoparticle arrays

In this paper, a systematic design and analysis of thin film crystalline silicon solar cells decorated with bilayer silver nanoparticles with different particle dimensions is presented. The particles are located on the rear of the solar cell. Using numerical simulations, we showed that the light absorption is enhanced when the particle radii of the upper layer Ag NPs is less than that of the lower. Moreover, our proposed structure showed a 9.97% increase in short-circuit current density and a 9.94% increase in intergraded quantum efficiency across the solar spectrum compared with the optimized counterpart decorated with uniform Ag NPs.

Light trapping enhancement induced by bimetallic non-alloyed nanoparticles on a disordered subwavelength flexible thin film crystalline silicon substrate using metal-assisted chemical etching.

We report the application of gold and silver (AuAg) bimetallic non-alloyed nanoparticles (BNNPs) on disordered subwavelength structures (d-SWSs). The combined advantages of the plasmonic structures and d-SWSs improved the light trapping performance of flexible thin film crystalline silicon (c-Si) solar cells. Antireflective d-SWSs were fabricated using spin-coated Ag ink and subsequent metal-assisted chemical etching, which reduced the ion-induced surface damage produced by the dry etching process. The dimensions of the d-SWSs were finely tuned by adjusting the Ag ink ratio. Au8Ag8 BNNPs were employed on optimized d-SWSs to achieve low reflectance at broadband wavelengths. The Au8Ag8 BNNPs on the d-SWSs showed 180% and 145% enhanced absorption compared to bare c-Si film and Au8Ag8 BNNPs on c-Si film, respectively, in the wavelength range of 300-1100 nm. After 200 cycles of bending the antireflection of the structures remained similar to the original level. This study introduces new approaches for light management in flexible thin film c-Si solar cells over the broadband wavelength range.

Design rules for net absorption enhancement in pseudo-disordered photonic crystal for thin film solar cells.

The role of pseudo-disordered photonic crystals on the absorption efficiency of simplified thin film crystalline silicon solar cells is presented and discussed. The expected short circuit current can thus be further increased compared to a fully optimized square lattice of holes, thanks to carefully controlled positions of the nanoholes in the considered realistic simplified solar cell stack. In addition, the pseudo-disordered structures are less sensitive to the angle of incidence, especially in the long wavelength range.

Time-resolved Photoluminescence for the Measurement of the Effective Carrier Lifetime in Si Photonic Structures

Two-dimensional photonic structures for advanced light trapping in thin film crystalline silicon solar cells are mainly studied from the optical point of view. However, the nanopatterning process can induce etching damage that can reduce the minority carrier lifetime and the cell performance. Time-resolved photoluminescence is used to evaluate the effect of photonic structures on the effective lifetime of nanopatterned silicon epi-layers. Two excitation wavelengths are used to evaluate separately the quality of the bulk and the patterned surface of the epi-layers. The measurements are discussed in connection with the carrier generation maps calculated with Finite-Difference Time Domain simulations.

Analysis of photo-current potentials and losses in thin film crystalline silicon solar cells

We present a detailed analysis of the photo-current potentials and losses in thin film crystalline silicon solar cells on glass. The effects of texturing the silicon backside, applying a diffuse back reflector and a textured anti-reflection foil were analysed. Light beam induced current measurements were used to determine the losses due to local effects like the absorber contact, cracks in the absorber and grain boundaries. Detailed loss analysis in combination with ray-tracing simulations showed that the maximum light trapping potential imposed by geometrical optics has nearly been achieved. The photocurrent losses due to incomplete carrier collection and parasitic absorption were accounted for using a theoretical model. For the investigated, textured, n-doped cell with reflector and anti-reflection foil, the short circuit current density (JSC) was 28.9mA/cm2 and the main loss factors were direct reflection (3.4mA/cm2), electrical shading effects due to the absorber contact (3.1mA/cm2) and incomplete carrier collection due to surface/bulk recombination (1.6mA/cm2). Using the presented light trapping scheme we obtained the following efficiencies: 11.8% for a p-doped and 12.1% for an n-doped crystalline silicon absorber. Finally, the potentials for efficiencies beyond 14% are discussed.

Multilayer silver nanoparticles for light trapping in thin film solar cells

In this paper, a systematic design and analysis of thin film crystalline silicon solar cells incorporated with a new style of multilayer silver (Ag) nanoparticles (NPs) array is presented. Using numerical simulations, we showed that multilayer Ag NPs provide better light trapping than single layer Ag NPs when the Ag NPs are located on the rear of the solar cell. Furthermore, Ag NP double layers on the rear achieved the best light absorption enhancement for solar cells. Ag NP double layers showed a 6.65% increase in intergraded quantum efficiency across the solar spectrum compared with single layer structures. The parasitic absorption occurring in Ag NP bottom layers was also discussed.

“Silicon millefeuille”: From a silicon wafer to multiple thin crystalline films in a single step

During the last years, many techniques have been developed to obtain thin crystalline films from commercial silicon ingots. Large market applications are foreseen in the photovoltaic field, where important cost reductions are predicted, and also in advanced microelectronics technologies as three-dimensional integration, system on foil, or silicon interposers [Dross et al., Prog. Photovoltaics 20, 770-784 (2012); R. Brendel, Thin Film Crystalline Silicon Solar Cells (Wiley-VCH, Weinheim, Germany 2003); J. N. Burghartz, Ultra-Thin Chip Technology and Applications (Springer Science + Business Media, NY, USA, 2010)]. Existing methods produce “one at a time” silicon layers, once one thin film is obtained, the complete process is repeated to obtain the next layer. Here, we describe a technology that, from a single crystalline silicon wafer, produces a large number of crystalline films with controlled thickness in a single technological step.

Front side plasmonic effect on thin silicon epitaxial solar cells

We study the effect of metal nanoparticles, showing localised plasmonic resonances, on the spectrally resolved efficiency of thin film crystalline silicon solar cells. We investigate model structures: silver (Ag) nanodiscs on the surface of epitaxial cells grown on highly doped silicon substrates, with a controlled micron-scale thickness. The cells have no back reflector in order to exclusively study the effect of the front surface on their optical properties. The nanodiscs were deposited through hole-mask colloidal lithography, which is a low-cost, bottom-up and extremely versatile technique. As opposed to many other works, we use as benchmarks both bare silicon cells and cells with a dielectric antireflection coating. We optically observe a resonance showing an absorption increase, found to be controllable by the discs parameters. We also see an increase in short-circuit current with respect to bare cells, but we see a decrease in efficiency with respect to cells with a dielectric antireflection coating, due to losses at short wavelengths. As the material properties are not notably affected by the particles deposition, we show that the main loss mechanisms are an important parasitic absorption in the nanoparticles and destructive interferences.

Thin film silicon solar cells by AIC on foreign substrates

This paper presents the fabrication of thin film crystalline silicon solar cells on foreign substrates like alumina, glass–ceramic (GC) and metallic foils (ferritic steel—FS) using seed layer approach, which employs aluminium induced crystallisation (AIC) of amorphous silicon. Effect of hydrogen content in a-Si:H precursor films on the AIC process has been studied and the results showed that defects in the AIC grown films increased with increase of hydrogen content. At the optimal thermal annealing conditions, the AIC grown poly-Si films showed an average grain size of 7.6, 26, and 8.1 μm for the films synthesised on alumina, GC, and FS, respectively. The grains were (1 0 0) oriented with a sharp Raman peak around 520 cm −1. Similarly, n-type seed layers were also fabricated by over-doping of as-grown AIC layers using a highly phosphorus doped glass solution. The resistivity of as-grown films reduced from 8.4×10 −2 Ω cm (p-type) to 4.1×10 −4 Ω cm (n-type) after phosphorus diffusion. These seed layers of n-type/p-type were thickened to form an absorber layer by vapour phase epitaxy or solid phase epitaxy. The passivation step was applied before the heterojunction formation, while it was after in the case of homojunction. Open circuit voltage of the junctions showed a strong dependence on the hydrogenation temperature and microwave (μW) power of electron cyclotron resonance (ECR) plasma of hydrogen. Effective passivation was achieved at a μW power of 650 W and hydrogenation temperature of 400 °C. Higher values of solar conversion efficiencies of 5% and 2.9% were achieved for the n-type and p-type heterojunction cells, respectively fabricated on alumina substrates. The analysis of the results and limiting factors are discussed in detail.

Thin silicon films synthesis by AIC on ONO coated metal foils

Abstract Thin film crystalline silicon solar cells on flexible metallic substrates are being considered to be potential for low cost production. In the present investigation, metallic substrates (MS) coated with dielectric diffusion barrier layer (BL) of ONO (SiO 2 /SiN/SiO 2 ) have been used for the fabrication of polycrystalline silicon ( pc -Si) thin films using aluminium induced crystallisation (AIC) for the first time. The crystallographic quality of pc -Si layers synthesised by AIC has been studied using Raman and UV reflection spectroscopy. Similarly, grain size and defect distribution were characterised using electron backscattered diffraction (EBSD) analysis. The AIC grown films showed a symmetric peak around 519–520 cm −1 with an average grain size of 8.1 μm. The thermal stability of the diffusion barrier has been evaluated by annealing the structure, MS/BL/ pc -Si, at higher temperatures with subsequent chemical analysis of AIC grown pc -Si template. The potential impurities are identified to be Fe and Ni on a limited area. These results open the potential of fabrication of large grain silicon seed layer on flexible substrates for thin film solar cells technology.

Epitaxially grown emitters for thin film crystalline silicon solar cells

In recent years, research on epitaxial growth for thin film crystalline silicon solar cells has gained in importance due to the alarming feedstock shortage of electronic grade polysilicon. This work concentrates on the epitaxial growth of the emitter, as a replacement for emitter diffusion, on top of an epitaxially grown base. The main advantage of emitter formation by CVD is more controllable doping profile, which gives the opportunity to form an excellent front surface field, leading to high open-circuit voltages. In this paper, the doping profile and thickness of the epitaxial layers are optimized. A solar cell process including a light trapping mechanism resulted in solar cell efficiencies close to 15%.

Simulation and implementation of a porous silicon reflector for epitaxial silicon solar cells

AbstractOne of the main challenges in the ongoing development of thin film crystalline silicon solar cells on a supporting silicon substrate is the implementation of a long‐wavelength reflector at the interface between the epitaxial layer and the substrate. IMEC has developed such a reflector based on electrochemical anodization of silicon to create a multi‐layer porous silicon stack with alternating high and low porosity layers. This innovation results in a 1–2% absolute increase in efficiency for screenprinted epitaxial cells with a record of 13·8%. To reach a better understanding of the reflector and to aid in its continued optimization, several extensive optical simulations have been performed using an in‐house‐developed optical software programme. This software is written as a Microsoft Excel workbook to make use of its user‐friendliness and modular structure. It can handle up to 15 individual dielectric layers and is used to determine the influence of the number and the sequence of the layers on the internal reflection. A sensitivity analysis is also presented. A study of the angle at which the light strikes the reflector shows separate regions in the physical working of the reflector which include a region where the Bragg effect is dominant as well as a region where total internal reflection plays the largest role. The existence of these regions is proved using reflection measurements. Based on these findings, an estimate is made for the achievable current gain with an ideal reflector and the potential of epitaxial silicon solar cells is determined. Copyright © 2008 John Wiley & Sons, Ltd.

A thin-film silicon solar cell and module

AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract We have developed a new light-trapping scheme for a thin-film Si stacked module (Si HYBRID PULS module), where a (a-Si:H/transparent interlayer/microcrystalline Si) thin-film was integrated into a large-area solar cell module. An initial aperture efficiency of 13·1% has been achieved for a 910 × 455 mm Si HYBRID PLUS module, which was independently confirmed by AIST. This is the first report of the independently confirmed efficiency of a large-area thin-film Si module with an interlayer. The 19% increase of short-circuit current of this module was obtained by the introduction of a transparent interlayer that caused internal light-trapping. A mini-module was shown to exhibit a stabilized efficiency of 12%. Outdoor performance of a Si HYBRID (a-Si:H / micro-crystalline Si stacked) solar cell module has been investigated for over 4 years with two different kinds of module (top and bottom cell limited, respectively). The HYBRID modules limited by the top cell have exhibited a more efficient performance than the modules limited by the bottom cell, in natural sunlight at noon. Copyright © 2005 John Wiley & Sons, Ltd. REFERENCES 1 Yamamoto K, Suzuki T, Yoshimi M, Nakajima A. Low temperature fabrication of thin film polycrystalline Si solar cell on the glass substrate and its application to the a-Si:H/Polycrystalline Si tandem solar cell. Proceedings of the 25th IEEE Photovoltaic Energy Conversion, Conference, 1996; 661– 664. 2 Yamamoto K, Yoshimi M, Suzuki T, Tawada Y, Okamoto Y, Nakajima A. Very thin film crystalline silicon solar cells on glass substrate fabricated at low temperature. IEEE Transactions Electron Devices 1999; 46: 2041– 2047. 3 Yamamoto K, Yoshimi M, Tawada Y, Okamoto Y, Nakajima A. Cost effective and high-performance thin film Si solar cell towards the 21st century. Solar Energy Materials and Solar Cells 2001; 66: 117– 125. 4 Meier J, et al. On the way towards high-efficiency thin film silicon solar cells by the ‘micromorph’ concept. Proceedings of the Material, Research Society Symposium, Spring Meeting, San Francisco, 1996; 420: 3– 14. 5 Yamamoto K, et al. Novel HYBRID thin film silicon solar cell and module. Proceedings of the 3rd World Conference on Photovoltaic Solar Energy Conversion, 2003; Paper S20B903. 6 Nakajima A, et al. Improvement on actual output power of thin film silicon HYBRID module. Proceedings of the 3rd World Conference on Photovoltaic Solar Energy Conversion, 2003; Paper 60B1104. Citing Literature Volume13, Issue6September 2005Pages 489-494 ReferencesRelatedInformation

CRYSTALLINE SILICON BASED PHOTOVOLTAICS: TECHNOLOGY AND MARKET TRENDS

An overview is given concerning industrial technologies, IMECS's advanced pilot line crystalline silicon solar cell technologies and medium term developments for industrial crystalline silicon terrestrial solar cell fabrication. Also IMEC's work on thin film crystalline silicon solar cells is shortly presented, all of this taking into account the existing market and technology trends.

Large-grained polycrystalline Si films obtained by selective nucleation and solid phase epitaxy

We investigated the formation of large-grain polycrystalline silicon films on glass substrates for application in low-cost thin film crystalline silicon solar cells. Since the use of glass substrates constrains process temperatures, our chosen approach to form large-grain polycrystalline silicon templates is selective nucleation and solid phase epitaxy (SNSPE). In this process, selective crystallization of an initially amorphous silicon film, at lithographically predetermined sites, enables grain sizes larger than those observed via random crystallization. Selective heterogeneous nucleation centers were created for both P-doped, B-doped and undoped, 100 nm thick amorphous silicon films, by masked implantation of In or Ni islands, followed by annealing at temperatures below 600°C. Seeded crystallization begins at the metal islands and continues via lateral solid phase epitaxy (SPE), thus obtaining crystallized regions of several tens of square microns. The maximum achievable grain size depends on the product of the SPE rate and the incubation time for the spontaneous nucleation. We have studied the dependence of the SPE rate and the incubation time on the type of metal (In and Ni) inducing the nucleation and on the electronic dopant (e.g. P and B) concentration in the 10 19–10 21 cm −3 range.

Very thin film crystalline silicon solar cells on glass substrate fabricated at low temperature

The performances of thin-film poly-Si solar cells with a thickness of less than 5 /spl mu/m on a glass substrate have been investigated. The cell of glass/back reflector/n-i-p-type Si/ITO is well characterized by the structure of naturally surface texture and enhanced absorption with a back reflector (STAR), where the active i-type poly-Si laser was fabricated by plasma chemical vapor deposition (CVD) at low temperature. The cell with a thickness of 2.0 /spl mu/m demonstrated an intrinsic efficiency of 10.7% (aperture 10.1%), the open-circuit voltage of 0.539 V and the short current density of 25.8 mA/cm/sup 2/ as independently confirmed by Japan Quality Assurance, which shows the no clear light-induced degradation. The optical and transport properties of poly Si cells are summarized.

Ni-Induced Selective Nucleation and Solid Phase Epitaxy of Large-Grained Poly-Si on Glass

AbstractWe investigated the formation of large-grain polycrystalline silicon films on glass substrates for application in low-cost thin film crystalline silicon solar cells. Since use of glass substrates constrains process temperatures, our approach to form large-grain polycrystalline silicon templates is selective nucleation and solid phase epitaxy (SNSPE). In this process, selective crystallization of an initially amorphous silicon film, at lithographically predetermined sites, enables grain sizes larger than those observed via random crystallization. Selective heterogeneous nucleation centers were created on undoped, 75 nm thick, amorphous silicon films, by masked implantation of Ni islands, followed by annealing at temperatures below 600 °. At this temperature, the Ni precipitates into NiSi2 particles that catalyze the transition from the amorphous to the crystalline Si phase. Seeded crystallization begins at the metal islands and continues via lateral solid phase epitaxy (SPE), thus obtaining crystallized regions of several tens of square microns in one hour. We have studied the dependence of the crystallization rate on the Ni-implanted dose in the seed, in the 5×1015/cm3 - 1016/cm3range. The large grained polycrystalline Si films were then used as a substrate for molecular beam epitaxy (MBE) depositions of 1 [.proportional]m thick Si layers. Transmission electron microscopy (TEM) analysis showed a strong correlation between the substrate morphology and the deposited layer. The layer presented a large grain morphology, with sizes of about 4 [.proportional]m.

Limits to the efficiency of silicon multilayer thin film solar cells

Thin film crystalline silicon solar cells can only achieve high efficiencies if light trapping can be used to give a long optical path length, while simultaneously achieving near unity collection probabilities for all generated carriers. This necessitates a supporting substrate of a foreign material, with refractive index compatible with light trapping schemes for the silicon. The resulting inability to nucleate growth of crystalline silicon films of good crystallographic quality on such foreign substrates, at present, prevents the achievement of high efficiency devices using conventional single junction solar cell structures. The parallel multijunction solar cell provides a new approach for achieving high efficiencies from very poor quality material, with near unity collection probabilities for all generated carriers achieved through appropriate junction spacing. Heavy doping is used to minimise the dark saturation current contribution from the layers, therefore allowing respectable voltages. The design strategy, corresponding advantages, theoretical predictions and experimental results are presented.