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Intellectual Property barriers to photvoltaic efficiency

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This is a literature review page for investigating on Intellectual Property (IP) barriers to Photovoltaic solar cells efficiency. It would be our pleasure if you share your experience in this area with us. (Discussion tab is top left of this page)


Meaning of Intellectual Property: Term of Intellectual Property (IP) refer to the rights that is given by the law to the person who create, innovate or designed a new thing. There are various types of IP such as trade market, copyright, patents, industrial design rights, all artistic works and much more. This phrase (IP) was used for the first time in 1769 but its most ever use refer to the end of 20th century till now. By this law inventors feel more secure to publish their work to the public because all benefits of that invention must refer to the inventor.Intellectual Property Wikipedia

Literature Review

The IP landscape for photovoltaics

Bauer, C. E., & Neuhaus, H. J. (2008, September). The IP landscape for photovoltaics. In Electronics System-Integration Technology Conference, 2008. ESTC 2008. 2nd (pp. 51-56). IEEE.

  • pv patent in us 1968-2008
  • patent applications
  • Principal categories in PV patents (Materials, Control, Manufacturing,..)

Business, market and intellectual property analysis of polymer solar cells

Nielsen TD, Cruickshank C, Foged S, Thorsen J, Krebs FC. Business, market and intellectual property analysis of polymer solar cells. Solar Energy Materials and Solar Cells. 2010 Oct;94(10):1553–71.

  • companies and markets, it seems easy to copy, risk for commercial motivation, Konarka is first in market, Probably has biggest patent portfolio
  • valuable patent search engines [82-84]
  • eminent universities and factories who own the most number of patent are introduced in section 4.8
  • 170 countries are member of Paris Convection and 140 of them have signed the Patent Cooperation Treaty (CPT)
  • Difference between Patent Application & Patent
  • First a patent is published in international mode then goes on national and then regional

Photovoltaic cell basic information

Photovoltaic Cell Conversion Efficiency Basics

these parameters have effect on PV cells efficiency

  • Wavelength of light: solar cell cannot absorb entire spectrum of sunlight. Photons with energy below the material bandgap cannot be absorbed and photons with higher energy, will loose their extra energy as heat or light.
  • Recombination: produced electrons and holes will recombine before contribute in cell's current.This can be due direct recombination, which electrons and hols meet each other randomly, or indirect recombination which is due to impurities, structure defects or surface recombination.
  • Natural resistance: this happen in bulk material, thin surface and contact point of panel to output circuit
  • Temperature: Almost all solar cells lose their efficiency by growing temperature. Considering the most part of incident sunlight convert to heat in solar cell, then operating temperature would be an issue for solar cells. operating T can be considered when designing the solar cells to be a good match or somehow manage to cool the panel for higher efficiency.
  • Reflection: A big portion of sunlight would be reflected on the solar cell surface (30%) if find a way to reduce the reflection, it means there would be more photon available to generate more electron-hole pairs and efficiency of light increases in result. Many methods are introduced to reduce the reflection such as anti reflection coating (multi layers) and texture the top surface of solar cell.
  • Electrical Resistance: It is obvious that by larger electrical contact, electrical resistance would reduce but on the other hand more incident light will be blocked. It means there is a trade off between size of metal contact on the surface and electrical resistance for solar cells. Nearly, new methods are being introduced to overcome this issue like using a very thin transparent metal contact all over the solar cell surface.

Photovoltaic technology development: A perspective from patent growth analysis

Liu JS, Kuan CH, Cha SC, Chuang WL, Gau GJ, Jeng JY. Photovoltaic technology development: A perspective from patent growth analysis. Solar Energy Materials and Solar Cells. 2011 Nov 30;95(11):3130-6.

  • In this paper is tried to find a direct relation between the crude oil price and the number of registered patents. In the graph he draw number of patent graph one year ahead (When the price of crude oil increase, more money will inject to the R&D in PV which will take time for a patent come out, in average one year)
  • In this paper very nicely a search strategy for relevant patent in PV is described in section 4
  • five different category for PV solar cells was achieved (1)Emerging PV include:polymer and dye-sensetive (2)Silicon include: bulk type and thin film silicon (3) CdTe (4)CIGS (5)Group III-V materials.
  • by the number of patent in these groups it is obvious that most focus of research are in category 1,2&5 and can see that scientist are not so much interested in categories 3&4
  • mentioned in this paper that there is a 10 years lag between PV market and its technology development.

Intellectual property rights and low carbon technology transfer: Conflicting discourses of diffusion and development

Ockwell DG, Haum R, Mallett A, Watson J. Intellectual property rights and low carbon technology transfer: Conflicting discourses of diffusion and development. Global Environmental Change. 2010 Oct 31;20(4):729-38.

  • Two sides of IP debates, one group believe this is kind of public good and must be supported by international funds and be accessible for developing countries like as drugs for treating HIV, in contrast, the other side they argue if developing countries be more serious in protecting IPR, the transfer technology would be much easier
  • Those groups which consider IP as a barrier are mostly from developing countries and those groups which consider IPR as a catalyst are from developed countries. U.S only had income $20 billion in 1995 for selling technology!
  • In continue in this paper mentioned in most cases developing countries had access to cutting-edge technologies but there were not enough funding to buy them or having competition in the market with those big eminent companies from developed countries

Intellectual property and access to clean energy technologies in developing countries

Barton JH. Intellectual property and access to clean energy technologies in developing countries. ICTSD Issue Paper. 2007 Dec;2.

  • In this paper tried to find out effects of IP on developing countries in three main sources of clean energy, PV, Wind and bio-mass
  • the conclusion in PV was: it cannot be considered as a barrier in developing countries (paper is for 2007) because there are some manufacturers which are eminent in the market which coming from developing countries such as Suntech Power Co., Ltd in 2006 it was the 4th biggest PV producer while it established in 2001, in continue he discus the main barrier would be competition in the market with those giant manufacturers who have most of the market in their control .

Innovation and international technology transfer: The case of the Chinese Photovoltaic industry

De La Tour A, Glachant M, Ménière Y. Innovation and international technology transfer: The case of the Chinese photovoltaic industry. Energy Policy. 2011 Feb 28;39(2):761-70. In this paper the main reasons that helped China in having a big role in the PV market is investigated.

  • mentioned china was successful only in downstream segment of PV production (Cells and assembling modules) which has many competitions in the market and benefit is not that much, while in upstream segment(silicon purification, ingot and wafer) still developed countries have the most part of the market
  • China did not invest so much on R&D compared to Japan or other developed countries in PV market but managed to buy ready firms, product line and technologies in the market
  • FDI (Foreign Direct Investment) also is another factor which is considered in this paper for a reason of improvement, it is true but its contribution in this success is not impressive

Placing a Glove on the Invisible Hand: How Intellectual Property Rights May Impede Innovation in Energy Research and Development (R& (and) D)

Sovacool BK. Placing a Glove on the Invisible Hand: How Intellectual Property Rights May Impede Innovation in Energy Research and Development (R& (and) D). Alb. LJ Sci. & Tech.. 2008;18:381.

  • At least there are four reasons to find out IP barriers in innovative energy technology:

(1):increasing energy demand and having fixed limited fossil fuel sources by oscillating prices (2): IP barriers affect both old and new technologies in energy market (3):If IP barriers truly avoiding diffusion of clean energy technology, then all attempts to promote developments in such technology would be Inconclusive till the barriers being addressed. experience from other market like, biotechnology, pharmacy and ... can be good example (4):to be familiar with new concept of innovation. there are three eminent arena in this field, 14000 industrial R&D laboratories, 730 governmental laboratories and 1270 universities facilities, the competition between theses three groups leads to some shifting in the concept of ownership, authorship, invention and also in organization section of innovation, production and diffusion technology.

  • In United states IP is classified into 6 areas (there are different views for this classification):

(1):Copyright. it is normally valid for the author's lifetime plus seventy years! (2):Patents are granted for new useful and non-obvious inventions. patents holder can has commercially use of patent for a limited time (usually 20 years). in U.s "first-to-invent" apply while in the rest of the world "first-to-file" apply. (3,4):trademarks and industrial design, very useful in automobiles and clothing industries (5): trade secrets (6):Geographical

  • the concept of Intellectual Property Rights (IPR): place monopolized rights to particular parties avoiding others to enter to their monopoly. this right can be transferred, licensed or mortgaged to third party.
  • If every body freely copy the product of a industry, it is true that the consumption price would reduce but on the other hand there would be no encouragement for new investigation for new technologies, then keeping monopoly of patent seems logic for a limited period of time to keep innovation competitive sens in the market.
  • Four categories that reveal the importance of patents: "invention motivation" "inducement of commercialization" "information disclosure" "exploration control"

Structural and economic barriers related to IPR and innovation

  • first, high transaction cost, which consist of a series inter related expenses such as pre application patent search, review of the product patent ability, preparation of formal drawings, filing fees with the U.S. Patent and Trademark Office (USPTO), and patent attorney fees. depending type of the technology and many other cases it start from $10,000 to hundreds of thousands dollars per patent. these cost also do not include continuation maintenance and enforcement against infringement costs. After filing the patent in U.S, it will cost around $20,000 for each other country that patent protection would apply. In addition, this process may takes between 24 and 36 months.
  • second, increasing the number of patents has direct and indirect influence in higher transaction cost. firms prefer to invest other parts of company than R&D because take huge time and energy to go through all patents and the risk of litigation is high.


Honsberg, C.B., Corkish, R.C. and Bremner, S.P., 2001. A new generalized detailed balance formulation to calculate solar cell efficiency limits.

  • Two ways to calculate solar efficiency - thermodynamics & detailed balance equation
  • both give same results
  • new detailed balance equation taking into consideration non ideal and non radiative processes
  • inclusion leads to higher efiiciencies


Swanson, R.M., 2005, January. Approaching the 29% limit efficiency of silicon solar cells. In Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE (pp. 889-894). IEEE

  • Thermodynamic ( shockley and queisser)- 30% efficiency black body, 33% efficiency AM1.5
  • Device modeling (improvements to improve efficiency)

-passivation -negative impact of band gap shrinkage -light trapping

  • auger recombination consideration gives 29%
  • optical losses ( Anti reflection coating, back surface reflector)
  • excess bulk recombination ( reduce crystal defects)
  • passivating and contact surfaces(gets the practical efficiency to 25%)
  • Other losses grid obstruction, grid series resistance, lower base lifetime, ITO series resistance and light absorption in the ITO

OPAL 2: Rapid Optical Simulation of Silicon Solar Cells

McIntosh, K.R. and Baker-Finch, S.C., 2012, June. OPAL 2: Rapid optical simulation of silicon solar cells. In Photovoltaic Specialists Conference (PVSC), 2012 38th IEEE (pp. 000265-000271). IEEE.

  • Antireflection coating and surface texture increases efficiency
  • ARC(introduces interference and increases thickness), surface texturing(multiple reflections on the front layer)
  • OPAL 1: accurately models multiple interactions of normally incident light with surface texture. Calculates Jo in underlying substrate so as to optimize ARC
  • OPAL 2: any incident angle and polarization, V groves, imperfect texture, incomplete texture
  • approach: 1)Ray tracing 2)Thin film calculation 3)current calculation
  • New morphology : hillocks and spherical caps

Anti-reflective coatings: A critical, in-depth review

Raut, H.K., Ganesh, V.A., Nair, A.S. and Ramakrishna, S., 2011. Anti-reflective coatings: A critical, in-depth review. Energy & Environmental Science, 4(10), pp.3779-3804.

  • Strategies: porous/patterned, gradient, effective medium theory
  • Requirements : broadband anti-reflectivity, omnidirectional anti reflectivity, polarization insensitivity
  • Types of ARC: TypeI(layer composition),TypeII(refractive index), Type III(surface topology)
  • Fabrication: Conventional-bottom up (solgel,glancing angle deposition, chemical vapor deposition),top down (etching) and Unconventional(lithography, micro replication technique)
  • Materials (Si based,TiO2 based, polymer based,gallium based, carbon based, organic)
  • Anti reflective coating on solar cells

PECVD of silicon nitride Si3N4 layers as antirefective coating


In order to absorb as much light as possible, it is necessary to minimize light reflection. This can be achieved by coating the solar cell with an antireflective layer ACR. When light waves reflected by the upper side and the lower side of the antireflection layer are interferring, then they can be cancelled. This happens, when the thickness of the anti-reflective layer is 1/4 of the wave length. Sunlight contains a broad range of different wave lengths and the angle of incidence also varies over the day. Therefore a compromis regarding the thickness of the ACR has to be found. Adaption of the refractive index of the antireflection coating can also help to optimize the layer. In solar technology, silicon nitride Si3N4 is used as antireflection layer. This layer causes the dark blue color of crystalline silicon solar cells. Deposition is carried out plasma-enhanced in a PECVD system (plasma enhanced chemical vapor deposition). PECVD technology allows a fast deposition of the silicon nitrid layer. Edge coverage is good. Usually, silane and ammonia are used as feedstock. Deposition can take place at temperatures below 400°C.

3 SiH4 + 4 NH3 → Si3N4 + 24 H2

Bulk and surface passivation of silicon solar cells accomplished by silicon nitride deposited on industrial scale by microwave PECVD

Soppe, W., Rieffe, H. and Weeber, A., 2005. Bulk and surface passivation of silicon solar cells accomplished by silicon nitride deposited on industrial scale by microwave PECVD. Progress in Photovoltaics: Research and Applications, 13(7), pp.551-569.

  • Amorphous silicon(SiNx:H) important in multicrystalline silicon solar cells.Three characteristics:
  • Good antrireflection coating
  • surface passivation made better by plasma enhanced chemical vapour deposition(PECVD)
  • Hydrogenation of wafer , the layer undergoes a short thermal treatment after breakdown
  • Cells produced with 16.8% efficiency by pilot inline PECVD process developed by ECN and Roth&Rau
  • Quality of SiNx:H layer depending on the optical properties , surface passivation, bulk passivation and production robustness
  • All three requirements fulfilled by using N2/SiH4 and NH3/SiH4

Optimised antireflection coatings for planar silicon solar cells using remote PECVD silicon nitride and porous silicon dioxide

Nagel, H., Aberle, A.G. and Hezel, R., 1999. Optimised antireflection coatings for planar silicon solar cells using remote PECVD silicon nitride and porous silicon dioxide. Progress in Photovoltaics: Research and Applications, 7(4), pp.245-260.

  • SiN film fabricated by remote plasma enhanced chemical vapour deposition
  • Excellent electronic surface passivation,antireflection coating
  • extinction coefficient increases with increase in refractive index hence optimization is necessary.
  • For optimal performance combine RPECVD SiN with porous SiO2
  • Refractive endices and extinction coefficients of RPECVD, porous SiO2, MgF2, TiOx,ZnS, B270 crown glass, soda lime glass, EVA with resin are determined.
  • Short circuit current for planar silicon solar cells covered by RPECVD SiN and/or porous SiO2 single and multi layers ARC is maximised for both glass encapsulated as well as nor encapsulated solar cells.
  • encapsulated solar cells have reduced short circuit currents as compared to non encapsulated ones due to higher extinction coefficieents at short wavelengths of embedding materials like EVA or resin and due to refection at the air/glass interface.Instead use single or double layer SiO2 on the outer surface of glass.
  • For non-encapsulated case, optimized AR coatings on the solar cells are universally suited for encapsulated conditions,regardless of the internal quantum efficiency of the cells.

Multilayer broadband anti-reflective coatings for bulk heterojunction polymer solar cells

[ Kaminski, P.M., Lisco, F., Bass, K., Barrows, A.T., Lidzey, D.G. and Walls, M., 2014. Multilayer broadband anti-reflective coatings for bulk heterojunction polymer solar cells.]

  • The coating consisted of four dielectric layers of alternating thin films of ZnO2 and SiO2.
  • The layers were deposited by using high rate pulsed DC magnetron sputtering using time only for nanometre thickness control.
  • Single layer limited efficiency, multi layered can use materials with refractive index higher than glass.
  • Usually alternating layers of SiO2 with metal oxides including zirconium dioxide(ZrO2),hafnium dioxide(HfO),titanium dioxide(TiO2),niobium pentoxide(Nb2O5) and tantalum pentoxide(TaO5).
  • Exceptional stability, thickness control enables interference control
  • WAR(weighted average reflection) reduced from 4.22% to below 1%
  • Short circuit current increased by 3.3%.

Realization of a near-perfect antireflection coating for silicon solar energy utilization

Kuo, M.L., Poxson, D.J., Kim, Y.S., Mont, F.W., Kim, J.K., Schubert, E.F. and Lin, S.Y., 2008. Realization of a near-perfect antireflection coating for silicon solar energy utilization. Optics letters, 33(21), pp.2527-2529.

  • single layer- reflectance only at specific angles, double layer- for a range of wavelength, artificially modified surface structure- alternate sub wavelength structure
  • relection<1% for wavelenthg 0.2-2.5um
  • multi layer graded refractive index profile : depends on smoothness of index profile, differential reflectance at each interface minimized, minimization doesn't dpend on wavelength and angle of incidence
  • graded index nanostructure
  • n(z)= n(min)+(n(max)+n(min))(10z3-15z4+6z5)
  • oblique angle deposition, controlled process to produce n=1.04-2.6, bottom TiO2 middle sputtered with SiO2 and TiO2,top two slanted SiO2 nanorods.
  • Si optical transparency at wavelength 1150nm.
  • reflectance = 1-6% for all visible and near IR wavelengths
  • all angles(8-60) reflectance is very low.
  • avg reflectance bare silicon(32.60%), wavelength/4(18.8%), graded (3.19)
  • efficiency increased from 20.5 to 42.7% by going from wavelength/4 to seven layer graded refractive index AR coating.

Nanostructured ZnO as biomimetic anti-reflective coatings on textured silicon using a continuous solution process

Han, S.Y., Paul, B.K. and Chang, C.H., 2012. Nanostructured ZnO as biomimetic anti-reflective coatings on textured silicon using a continuous solution process. Journal of Materials Chemistry, 22(43), pp.22906-22912.

  • microreactor assisted nanomaterial deposition (MAND)- microreaction+solution phase nanomaterial synthesis and film deposition
  • ZnO antireflection coating on tectured substrate from aqueous solution
  • based on night flying moth eye structure.
  • more easily scalable then conventional solution based process.
  • more environmentally friendly .
  • ZnO deposited a pyramidal Si surface.
  • well-aligned ZnO nanorod arrays were successfully fabricated on a textured silicon surface. The ZnO nanorod arrays were deposited on Ag NP seeds using microreactor-assisted nanoparticle deposition (MAND) process. The ZnO nanorod arrays on the textured surface are well aligned, nearly perpendicular to the silicon surface, and show a high density. The dense nanorod arrays significantly reduced the reflectance of the textured silicon surface down to 3.4%. The MAND process offered precise control over the level of supersaturation and the ability to deliver a constant flux of reactant solutions continuously. These features result in a rather fast growth rate (500 nm in 4 minutes) in contrast to previously reported ZnO nanowire growth (e.g. hours). This increase in manufacturing throughput is particularly important for solar cells.
  • The MAND process offers a more uniform and better controlled surface morphology along with lower cost and green, environmentally friendly processing than other ZnO nanowire growth processes like batch hydrothermal method or vapor transport processes. High crystalline nanostructured ZnO growth was achieved by MAND at a low process temperature of 70 °C and all growth processes in this study were conducted in an aqueous solution.