Periodic Structures for Improved Light Management in Thin-film Silicon Solar Cells

AbstractAdvanced light management in thin-film solar cells is important in order to improve the photo-current and, thus, to raise up the conversion efficiencies of the solar cells. In this article two types of periodic structures ¡V one-dimensional diffraction gratings and photonic crystals,are analyzed in the direction of showing their potential for improved light trapping in thin-film silicon solar cells. The anti-reflective effects and enhanced scattering at the gratings with the triangular and rectangular features are studied by means of two-dimensional optical simulations. Simulations of the complete microcrystalline solar cell incorporating the gratings at all interfaces are presented. Critical optical issues to be overcome for achieving the performances of the cells with the optimized randomly textured interfaces are pointed out. Reflectance measurements for the designed 12 layer photonic crystal stack consisting of amorphous silicon nitride and amorphous silicon layers are presented and compared with the simulations. High reflectance (up to 99 %) of the stack is measured for a broad wavelength spectrum. By means of optical simulations the potential for using a simple photonic crystal structure as a back reflector in an amorphous silicon solar cell is demonstrated.

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Improved light trapping effect for thin-film silicon solar cells fabricated on double-textured white glass substrate

Canadian Journal of Physics ◽

10.1139/cjp-2013-0621 ◽

2014 ◽

Vol 92 (7/8) ◽

pp. 920-923 ◽

Cited By ~ 6

Author(s):

Hidetoshi Wada ◽

Keiichi Nishikubo ◽

Porponth Sichanugrist ◽

Makoto Konagai

Keyword(s):

Thin Film ◽

Solar Cells ◽

Solar Cell ◽

Light Trapping ◽

Short Circuit ◽

Silicon Solar Cells ◽

Organic Chemical ◽

Trapping Effect ◽

Thin Film Silicon ◽

Vapor Deposition Technique

Light trapping effect using rough surface transparent conductive oxide (TCO) is one of the best ways to achieve high efficiency thin-film silicon solar cells. Several types of rough ZnO film fabricated by metal organic chemical vapor deposition technique onto the glass, which are etched by reactive ion etching, have been proposed so far as promising TCO substrates. In this paper, newly developed ZnO substrate with extremely high light scattering property comparing with typical pyramidal texture one was developed. By applying this newly developed ZnO substrate to the solar cell, higher short circuit current of about 2% has been achieved comparing with typical pyramidal texture one without sacrificing other parameters. This result showed that the newly developed substrate is suitable as a front TCO substrate for high performance thin-film silicon solar cell.

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Disorder Improves Light Absorption in Thin Film Silicon Solar Cells with Hybrid Light Trapping Structure

International Journal of Optics ◽

10.1155/2016/9371608 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

Yanpeng Shi ◽

Xiaodong Wang ◽

Fuhua Yang

Keyword(s):

Thin Film ◽

Solar Cells ◽

Periodic Structures ◽

Light Trapping ◽

Random Effect ◽

Large Field ◽

Silicon Solar Cells ◽

Trapping Effect ◽

Thin Film Silicon ◽

The Impact

We present a systematic simulation study on the impact of disorder in thin film silicon solar cells with hybrid light trapping structure. For the periodical structures introducing certain randomness in some parameters, the nanophotonic light trapping effect is demonstrated to be superior to their periodic counterparts. The nanophotonic light trapping effect can be associated with the increased modes induced by the structural disorders. Our study is a systematic proof that certain disorder is conceptually an advantage for nanophotonic light trapping concepts in thin film solar cells. The result is relevant to the large field of research on nanophotonic light trapping which currently investigates and prototypes a number of new concepts including disordered periodic and quasiperiodic textures. The random effect on the shape of the pattern (position, height, and radius) investigated in this paper could be a good approach to estimate the influence of experimental inaccuracies for periodic or quasi-periodic structures.

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Modeling of Advanced Light Trapping Approaches in Thin-Film Silicon Solar Cells

MRS Proceedings ◽

10.1557/opl.2011.955 ◽

2011 ◽

Vol 1321 ◽

Cited By ~ 4

Author(s):

Miro Zeman ◽

Olindo Isabella ◽

Klaus Jäger ◽

Pavel Babal ◽

Serge Solntsev ◽

...

Keyword(s):

Thin Film ◽

Zinc Oxide ◽

Solar Cells ◽

Solar Cell ◽

Light Trapping ◽

Spherical Particles ◽

Silicon Solar Cells ◽

Amorphous Silicon Solar Cell ◽

Thin Film Silicon ◽

Negative Effect

ABSTRACTDue to the increasing complexity of thin-film silicon solar cells, the role of computer modeling for analyzing and designing these devices becomes increasingly important. The ASA program was used to study two of these advanced devices. The simulations of an amorphous silicon solar cell with silver nanoparticles embedded in a zinc oxide back reflector demonstrated the negative effect of the parasitic absorption in the particles. When using optical properties of perfectly spherical particles a modest enhancement in the external quantum efficiency was found. The simulations of a tandem micromorph solar cell, in which a zinc oxide based photonic crystal-like multilayer was incorporated as an intermediate reflector (IR), demonstrated that the IR resulted in an enhanced photocurrent in the top cell and could be used to optimize the current matching of the top and bottom cell.

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Novel approaches of light management in thin-film silicon solar cells

MRS Proceedings ◽

10.1557/proc-0910-a25-01 ◽

2006 ◽

Vol 910 ◽

Cited By ~ 12

Author(s):

Janez Krc ◽

M. Zeman ◽

A. Campa ◽

F. Smole ◽

M. Topic

Keyword(s):

Thin Film ◽

Solar Cells ◽

Solar Cell ◽

Photonic Crystal ◽

Amorphous Silicon ◽

Wavelength Region ◽

Silicon Solar Cells ◽

Novel Approaches ◽

Back Reflector ◽

High Reflectance

AbstractIn order to improve light trapping in thin-film silicon solar cells two novel approaches are investigated in this article: angle-selective management of light scattering inside the solar cell and wavelength-selective manipulation of high reflectance or transmittance of light. Diffraction gratings are analyzed as a representative of the first approach. Haze and angular distribution function of scattered (diffracted) light in reflection are measured for aluminum-based rectangular periodic gratings with different period and height of the rectangles. High haze values in specific wavelength region and scattering angles of the investigated gratings measured in air and water agree very well with the theoretical predictions. Considering the actual optical situation in microcrystalline silicon solar cells, optimal period and height of the rectangular gratings applied as a back reflector are calculated for obtaining the total reflection at the front interfaces. In the frame of the second approach, photonic-crystal-like structures are introduced. By means of optical simulations photonic-crystal-like structures are investigated for two possible applications: an intermediate reflector in a micromorph silicon solar cell with wavelength-selective reflectivity and a dielectric back reflector with a high reflectance in the long-wavelength region. The photonic crystal structure consisting of sequences of n-doped amorphous silicon and ZnO layers is designed for the efficient intermediate reflector. For the back reflector with a high reflectance the structures with intrinsic amorphous silicon, SiO2, MgF2 and TiO2 are proposed.

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Light Trapping in Thin-Film Silicon Solar Cells with Periodic Structures

2006 IEEE 4th World Conference on Photovoltaic Energy Conference ◽

10.1109/wcpec.2006.279757 ◽

2006 ◽

Cited By ~ 2

Author(s):

Christian Haase ◽

Helmut Stiebig

Keyword(s):

Thin Film ◽

Solar Cells ◽

Periodic Structures ◽

Light Trapping ◽

Silicon Solar Cells ◽

Thin Film Silicon

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Light trapping in amorphous silicon solar cells on plastic substrates

MRS Proceedings ◽

10.1557/proc-769-h6.14 ◽

2003 ◽

Vol 769 ◽

Cited By ~ 2

Author(s):

Vanessa Terrazzoni-Daudrix ◽

Joelle Guillet ◽

Xavier Niquille ◽

Arvind Shah ◽

R. Morf ◽

...

Keyword(s):

Thin Film ◽

Solar Cells ◽

Amorphous Silicon ◽

Theoretical Calculations ◽

Light Trapping ◽

Production Costs ◽

Silicon Solar Cells ◽

Plastic Substrates ◽

Trapping Effect ◽

Thin Film Silicon

AbstractIn order to simultaneously decrease the production costs of thin film silicon solar cells and obtain higher performances, the authors have studied the possibility to increase the light trapping effect within thin film silicon solar cells deposited on flexible plastic substrates. In this context, different nano-structure shapes useable for the back contacts of amorphous silicon solar cells on plastic substrates have been investigated: random textures and gratings.The optimisation of such back reflectors is so far empirical. Gratings constitute a well-known optical technique and their light trapping effect can be optimised by simulation.A first conclusion is that neither the traditional “Haze factor” determined in air for a wavelength of 650nm nor the “rms roughness” of the surfaces are sufficient as criteria to optimise the back contact roughness for light trapping in cells. The shape of grains is a further essential criterion. The authors have so far obtained a relative current enhancement of 16% for solar cells deposited on randomly textured polyethylene terephthalate (PET) as compared to a corresponding conventional solar cell co-deposited on a flat mirror (Ag) on glass. Solar cells on PET with 6.3% stabilized efficiency have until now been obtained. Theoretical calculations indicate that gratings can enhance the current of a-Si solar cells by up to 30 percent.

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Optical and electrical modeling of thin-film silicon solar cells

Journal of Materials Research ◽

10.1557/jmr.2008.0125 ◽

2008 ◽

Vol 23 (4) ◽

pp. 889-898 ◽

Cited By ~ 68

Author(s):

M. Zeman ◽

J. Krc

Keyword(s):

Thin Film ◽

Solar Cells ◽

Solar Cell ◽

Amorphous Silicon ◽

Triple Junction ◽

Silicon Germanium ◽

Buffer Layers ◽

Silicon Solar Cells ◽

Antireflective Coatings ◽

Thin Film Silicon

This article focuses on the modeling and simulation of thin-film silicon solar cells to obtain increased efficiency. Computer simulations were used to study the performance limits of tandem and triple-junction, silicon-based solar cells. For the analysis, the optical simulator SunShine, which was developed at Ljubljana University, and the optoelectrical simulator ASA, which was developed at Delft University of Technology, were used. After calibration with realistic optical and electrical parameters, we used these simulators to study the scattering properties required, the absorption in nonactive layers, antireflective coatings, and the crucial role of the wavelength-selective intermediate reflector on the performance of the solar cells. Careful current matching was carried out to explore whether a high photocurrent [i.e., more than 15 mA/cm2 for a tandem hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon (μc-Si:H) solar cell and 11 mA/cm2 for a triple-junction a-Si:H/amorphous silicon germanium (a-SiGe:H)/μc-Si:H solar cell] could be obtained. In simulations, the extraction of the charge carriers, the open-circuit voltage, and the fill factor of these solar cells were improved by optimizing the electrical properties of the layers and the interfaces: a p-doped, a-SiC layer with a larger band gap (EG > 2 eV) and buffer layers at p/i interfaces were used. Simulations demonstrated that a-Si:H/μc-Si:H solar cells could be obtained with a conversion efficiency of 15% or higher, and triple-junction a-Si:H/a-SiGe:H/μc-Si:H solar cells with an efficiency of 17%.

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Nanoimprint Lithography of Light Trapping Structures in Sol-gel Coatings for Thin Film Silicon Solar Cells

MRS Proceedings ◽

10.1557/proc-1101-kk13-05 ◽

2008 ◽

Vol 1101 ◽

Author(s):

Maurits Heijna ◽

Jochen Loffler ◽

Bas Van Aken ◽

Wim Soppe ◽

Herman Borg ◽

...

Keyword(s):

Thin Film ◽

Solar Cells ◽

Solar Cell ◽

Barrier Layer ◽

Nanoimprint Lithography ◽

Light Trapping ◽

Silicon Solar Cells ◽

Metal Foil ◽

Periodic Patterns ◽

Thin Film Silicon

AbstractFor thin-film silicon solar cells, light trapping schemes are of uppermost importance to harvest all available sunlight. Typically, superstrates with randomly textured TCO front layers are used to scatter the light diffusively in pin-cells on glass. Here, we investigate methods to texture opaque substrates with both random and periodic textures, for use in nip-cells on metal foil. We applied an electrically insulating SiOx-polymer coating on a stainless steel substrate, and textured this barrier layer by nanoimprint. On this barrier layer the back contact is deposited for further use in the solar cell stack. Replication of masters with various random and periodic sub-micron patterns was tested, and, using scanning electron microscopy, replicas were found to compare well with the originals. The embossing of the barrier layer does not diminish its electrically isolating properties, and thus adds extra functionality to this layer. Masters with U-grooves of various sub-micrometer widths have been used to investigate the optimal dimensions of regular patterns for light trapping in the silicon layers. Angular reflection distributions were measured to evaluate the light scattering properties of both periodic and random patterns. These periodic patterns, comprising diffraction gratings, show promising results in scattering the light to specific angles, enhancing the total internal reflection in the solar cell.

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