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  • It is always underestimatedYou know about global warming, energy security, Our energy reserves has not changed since 20 years. A lot of rapid investment in nuclear energy Current oil consumption is equivalent to 3.2 million barrel a day in electricity, water, transportation and industry. Demands have increased by 27% over the last three years.2010 consumption 2 Million b/day2028 Projected consumption 8 Million b/day 2032 Electricity demands will trouble ; additional 80 GW Very challenging politically to decrease consumption rate.
  • Squeeze light into places less than 100th of a wavelength
  • Figure 3 | light scattering and trapping is very sensitive to particle shape. a, Fraction of light scattered into the substrate, divided by total scattered power, for different sizes and shapes of Ag particles on Si. Also plotted is the scattered fraction for a parallel electric dipole that is 10 nm from a Si substrate. b, Maximum path-length enhancement, according to a first-order geometrical model, for the same geometries as in a at a wavelength of 800 nm. Absorption within the particles is neglected for these calculations, and an ideal rear reflector is assumed. The line is a guide for the eye. Insets: (top left) angular distribution of scattered power for a parallel electric dipole that is 10 nm above a Si surface (red) and a Lambertianscatterer (blue); (lower right) geometry considered for calculating the path-length enhancement. Figure reproduced with permission: © 2008 AIP.
  • Other Potential low cost, Abundant, easy to process PV Materials that possibly can be integrated into batteries The maximum theoretical efficiency of different PV technologies, based on the Shockley-Queisser limit are shown in this figure. While CdTe and CIGS are amongst the semiconductors with the highest efficiencies, FeS2 and CZTS also have high efficiencies, and contain more abundant and economic elements.
  • New plasmonic solar-cell designs. a, Plasmonic tandem solar-cell geometry. Semiconductors with different bandgaps are stacked on top of each other, separated by a metal contact layer with a plasmonic nanostructure that couples different spectral bands of the solar spectrum into the corresponding semiconductor layer. b, Plasmonic quantum-dot solar cell designed for enhanced photoabsorption in ultrathin quantum-dot layers mediated by coupling to SPP modes propagating in the plane of the interface between Ag and the quantum-dot layer. Semiconductor quantum dots are embedded in a metal/insulator/metal SPP waveguide. c, Optical antenna array made from an axial heterostructure of metal and poly(3-hexylthiophene) (P3HT). Light is concentrated in the nanoscale gap between the two antenna arms, and photocurrent is generated in the P3HT semiconductor83. d, Array of coaxial holes in a metal film that support localized Fabry–Perot plasmon modes. The coaxial holes are filled with an inexpensive semiconductor with low minority carrier lifetime, and carriers are collected by the metal on the inner and outer sides of the coaxial structure. Field enhancements up to a factor of about 50 are possible and may serve to enhance nonlinear photovoltaic conversion effects8
  • Transcript

    • 1. PV PlasmonicsBurhan Saifaddin
    • 2. Outline• Motivation for Plamonics PV – 1$/cost – -problems with current PV technology • Efficiency should be more than 20% • Solar module more to the 0.50• Advantages of Plasmonics PV – Enable use of new materials as thinfilms. – Raise efficiency• Examples on Plasmonics Architectures
    • 3. Energy Challenge Oil Consumption and Production - 8% energy consumption 16 15 ? ? 14 Million Barrel per Day 12 12 10 10 8 8 Consumption 8 6 Production 3.2 3.6 4 Capacity 2 0 2010 2015 2028Current oil consumption is equivalent to 3.2 Strait of Hormuzmillion barrel a day inelectricity, water, transportation and industry.Demands have increased by 27% over the lastthree years. 2032 Electricity demands willtrouble ; additional 80 GW Very challengingpolitically to decrease consumption rate. Data is based on a speech by Hashim Yamani, president of King Burhan Saifaddin Presentation | ENSC S-175 | August 8, 2011 Page 3 Abdullah City for Atomic and Renewable Energy, at GCF 2011.
    • 4. What are Plasmons ?• Surface Plasmons: surface waves that propagate along the surface of a conductor.• Used to concentrate and channel light using subwaveleght microstructures.• Other applications: wavelength optics, microscopy, data storage, light generation, and biophontoics.Theory of Diffraction by Small Holes, Bethe, Phys. Rev. 1944.Extraordinary optical transmission through sub-wavelength hole array, Ebbesen, Nature 1998.
    • 5. Overview of Current Photovoltaics (PV)Minimum installed system cost for:Rooftops 6-8 $/Wp,Utility cost 5 $/Wp, DOE goal to reach total of 1$/Wp (without batteries) In 2012 Chinese Silicon based Module dominate the market Prices for module are expected to reach 0.7 $/Wp for module. Is this is the real cost ?! First solar 0.60-.55 by 2014 Stock price in 20083 Stock price ~39$ DOE, 2011 GreenTechMedia 5
    • 6. What can Plasmonics do to PV ? Decrease in materials cost by 10% can ,possibly, can reduce Solar Module by 0.1$/Wp 5 c/kWh 1 $/Wp~ 50B dollars industry based on generous Government subsides and ‘’biased’ regulations Burhan Saifaddin Presentation | ENSC S-175 | August 8, 2011 www.mckinsey.com/clientservice/ccsi/pdf/economics_of_solar.pdf Page 6
    • 7. solar cell. b, Schematic indicating carrier di usion from the region where photocarriers are generated to the p–n junction. Charge carriers generated taking into account integration with optimized anti-re ection coat- far away (more than the di usion length Ld) from the p–n junction are not ings, isbeing studied by several research groups. In recent papers38,39, e ectively collected, owing to bulk recombination (indicat ed by the asterisk). we reported that both shape and size of metal nanoparticles are key factors determining the incoupling e ciency. is is illustrated Plasmonics Light trapping guided modes in the semiconductor slab, whereupon the light is converted to photocarriers in the semiconductor (Fig. 2c). As will be discussed in detail in the next section, these three light-trapping techniques may allow considerable shrinkage in Fig. 3a, which shows that smaller particles, with their e ective dipole moment located closer to the semiconductor layer, couple a larger fraction of the incident light into the under lying semiconduc- tor because of enhanced near- eld coupling. Indeed, in the limit of (possibly 10- to 100-fold) of the photovoltaic layer thickness, while a point dipole very near to a silicon substrate, 96% of the incident keeping the optical absorption (and thus e ciency) constant. light is scattered into the substrate, demonstrating the power of a b c Figure 2 | Plasmonic light -trapping geometries for thin-film solar cells. a, Light trapping by scattering from metal nanoparticles at the surface of the solar cell. Light is preferentially scatt ered and trapped into the semiconductor thin film by multiple and high-angle scatt ering, causing an incr ease in the e ective Scattering Concentration surface plasmon polaritons optical path length in the cell. b, Light trapping by the excitation of localized surface plasmons in metal nanopar ticles embedded in the semiconductor. (SPPs) propagating The excited particles’ near-field causes the creation of electron–hole pairs in the semiconductor. c, Light trapping by the excitation of surf ace plasmon polaritons at the metal/ semiconductor interface. A corrugated metal back surface couples light t o surface plasmon polarit on or phot onic modes that propagate in the plane of the semiconductor layer. 206 NATURE MATERIALS | VOL 9 | MARCH 201 | www.nature.com/ naturematerials 0 Improve light absorption while 20 10 Macmillan Publishers Limited. All rights reserved © preserving high carrier collection which enable thinner active materialsnmat_2629_MAR10.indd 206 8/2/10 15:18:17 Plasmonics for improved photovoltaic devices. Atwater, Polman, Nat. Mat 2010.
    • 8. Light scattering and trapping is very sensitive to shape and of particles.NATURE MATERIALS DOI: 10.1038/ NMAT2629 REVIEW ARTICLE a 1 bREVIEW ARTICLE NATURE MATERIALS DOI: 10.1038/ NMAT2629 Parallel dipole 100 Maximum path-length enhancement 0.8 Lambertian Fraction scattered into substrate a Various additional ways of using plasmonic nanostructures to 1.6 Blue Green Red increase photovoltaic energy conversion are described in the section on other plasmonic solar-cell designs. Hemisphere 0.6 Si Plasmonic light trapping in thin-film solar cells Spectral intensity (W m2 nm–1) 1.2 Cylinder Light scattering using particle plasmons. Light scattering from a small metal nanoparticle embedded in a homogeneous medium 10 0.4 AM1 solar .5 Dipole is nearly symmetric in the forward and reverse directions27,28. is spectrumCylinder 0.8 situation changes when the particle is placed close to the interface nm Sphere 100 Hemisphere between two dielectrics, in which case light will scatter preferen- 0.2 Sphere 1 nm tially into the dielectric with the larger permittivity29. e scattered 00 2-µm-thick Sphere 1 nm 50 Sphere 1 nm 50 0.4 Si wafer light will then acquire an angular spread in the dielectric that e ec- tively increases the optical path length (see Fig. 2a). Moreover, light 0 scattered at an angle beyond the critical angle for re ection (16° for 1 500 550 600 650 700 750 the S 800i/air interface) will remain trapped in the cell. In addition, if 0.6 0.7 0.8 0.9 1 0 the cell has a re ecting metal back contact, light scattered into substrate 400 600 Wavelength (nm) 800 1,000 1,200 Fraction re ected towards Free-space wavelength (nm) the surface will couple to the nanoparticles and be partly reradi- ated into the wafer by the same scattering mechanism. As a result,Figure 3 | Light scattering and trapping is very sensitive to particle incidenta, Fraction of light scatt ered into the substrate, divided by total scattered the shape. light will pass several times through the semiconductor bpower, for di erent sizes and shapes of Ag par ticles on Si. Also plott edincreasing the e ective path length. lm, is the scatt ered fraction for a parallel electric dipole that is 1 nm from a Si 0 n For efficient exciton harvesting,substrate. b, Maximum path-length enhancement, according to a first-order geometrical model, f or the same geometries as in a at a wavelength of p e enhanced incoupling of light into semiconductor thin lms by scattering from plasmonic nanoparticles was rst recognized by800 L Materials thickness (or effective optical thickness) nm. Absorption within the par ticles is neglect ed for these calculations, and an ideal r ear reflector is assumed. The line is a guide f or the eye. Insets: d(top left) angular distribution of scatt ered power for a parallel electric dipoleHall, is 1 used denseananoparticle arrays asaresonant * S tuart and that who nm above Si surface (red) and Lambertian scatterer (blue); 0 scatterers to couple light into Si-on-insulator photodetector struc- * must be shorter than exciton diffusion length(lower right) geometry considered for calculating the path-leng thtures30,31. ey observedreproduced with permission: © 2008 AIP. enhancement. Figure a roughly 20-fold increase in the infrared photocurrent in such a structure. is research eld then remained relatively dormant for at back contact 45. Finally, in designing the particle scattering technique. Figure 3b shows the path-length with a many years, until applications in thin- lm optimized plasmonic enhancement in the solar cell derived from Fig. 3a usingsolar cells emerged, with papersarrays, we must takelight cou- a simple light-trapping published on enhanced into account coupling between Plasmonics for improved photovoltaic devices. pling into single-crystalline Si (ref. 32), amorphous Si (refs 33,34), rst-order scattering model. For 100-nm-diameter Ag hemispheres the nanoparticles, ohmic damping, cells cov- di raction e ects46 and Si-on-insulator 35, quantum well 36 and GaAs (ref. 37) solar gratingFigure 1 Optical absorption and carrier is found. ese light-trapping e ects the coupling Atwater, Polman, Nat. Mat 2010. on Si,| a 30-fold enhancement di usion requirements in a solar ered with metal nanoparticles. to waveguide modes47–49.cell. a, AM1 pronounced at the peak of theindicates the solar are most solar spectrum, together with a graph that plasmon resonance spec- there is now considerable experimental evidence that .5 Although
    • 9. that light is coupled into an S mode as well as a photonic mode PP Materials resources are a signi cant limitation for large-scale that propagates inside the S waveguide, and that the strength of i production of two of the most common thin- lm solar-cell mate- coupling to each mode can be controlled by the height of the scatter- rials: CdTe and CuInSe2. Manufacturing costs for these cells have Advantages of Plasmonics. ing object 66. e photonic modes are particularly interesting as they su er from only very small losses in the metal. e fraction of light coupled into both modes increases with increasing wavelength. is fallen, and solar-cell production using these semiconductors is expanding rapidly. Table 1 lists the (projected) annual solar-cell production per year, as well as the materials feedstock required for 1. Enable Thin films of Inexpensive materials is mainly because at shorter wavelengths the incoming light beam is directly absorbed in the S layer. e data demonstrate that light with i the production of the corresponding solar-cell volume using Si, CdTe or CuInSe2. As can be seen, the materials feedstock required with short exciton diffusion length and λ > 800 nm, which would not be well absorbed by normal incidence in 2020 exceeds the present annual world production of Te and In, on the S layer (see Fig. 1a), can now be e ciently absorbed by i and in the case of In is even close to the total reserve base. If it more defects. conversion into the in-plane S and photonic modes. Although PP were possible to reduce the cell thickness for such compound semi- this example shows coupling from a single, isolated ridge, the shape, conductor cells by 10–100 times as a result of plasmon-enhanced 2. Reduce dark current height and interparticle arrangements of incoupling structures can light absorption, this could considerably extend the reach of these all be optimized for preferential coupling to particular modes. In the compound semiconductor thin- lm solar cells towards the tera- 3. Increase photocurrent. ultimate, ultrathin Si solar cell (thickness <100 nm), no photonic watt scale. Earth-abundance considerations will also in uence 4. Possibly reduce cost. modes exist and all scattered light is converted into S PPs. Further enhancements are expected for three-dimensional scattering struc- plasmonic cell designs at large-scale production: although Ag and Au have been the metals of choice in most plasmonic designs and tures integrated in the back contact, and more research is required experiments, they are relatively scarce materials, so scalable designs to investigate this. Most recently, we have reported experiments on will need to focus on abundant metals such as Al and Cu. amorphousS thin- lm solar cellsdeposited on a textured metal back i Reducing the active-layer thickness by plasmonic light trap- re ector, which show a 26% enhancement in short-circuit current, ping not only reduces costs but also improves the electrical char- with the primary photocurrent enhancement in the near-infrared67. acteristics of the solar cell 78. First of all, reducing the cell thickness In relation to the plasmonic coupling e ect, a similar conversion reduces the dark current (I dark), causing the open-circuit voltage mechanism into surface polariton waves has recently been demon- Voc to increase, as Voc = (kBT/q) ln(I photo/I dark + 1), where kB is the strated using lossy dielectrics rather than metals68. Here too, light Boltzmann constant, T is temperature, q is the charge and I photo is is e ciently coupled into a two-dimensional wave that can then the photocurrent. Consequently, the cell e ciency rises in loga- be absorbed in a semiconductor layer. Several other reports on the rithmic proportion to the decrease in thickness, and is ultimately integration of S geometries with thin- lm solar-cell geometries PP are now appearing, including organic solar cells69–71. e data in Fig. 5b were calculated for light under normal inci- Table 1 | Photovoltaic resource requirements: materials by dence, with a polarization perpendicular to the ridge. e next production and reserve. challenge is to engineer coupling structures that depend weakly on Year Annual solar-cell Material frequency, polarization and angle of incidence. A two-dimensional production* Si (c-Si) Te (CdTe) In (CuInSe2) mesh structure with features much smaller than the wavelength 2000 0.3 GW p 4 0.03 0.03 may serve such a purpose. It is clear that with these scattering structures made on the rear 2005 1 GWp .5 15 0.15 0.15 side of the cell, the concepts of plasmonic scattering, concentra- 2020 50 GW p 150 5 5 tion and coupling from this section and the previous two sections World production 1,000 0.3 0.5 become closely integrated. Indeed, any solar cell with a non-planar (1,000 tonnes per year) metal back contact will have geometric scattering and higher local Reserve base (1,000 tonnes) Abundant 47 6 elds as well as scattering into photonic and plasmonic modes, and *Wp = peak output power under full solar illumination. all these e ects must be carefully engineered. We note that there is The annual solar-cell production and the required materials feedstock are indicated, assuming cells at present considerable activity on thin- lm solar cells with textured are made of Si, CdTe or CuInSe2. The assumed material use for Si is 1 g W p–1 in 2000, 1 g Wp–1 in 3 0 2005, 3 g Wp–1 in 2020 (projected); it is 0.1g Wp–1 for Te and In. The two bottom rows indicate the metal back re ectors for light trapping72–77.Also, help other short diffusion length quantum dots, organics, polycrys. semiconductors etc. world reserve base data for Si, Te and In (that is, resources that are economic at present or marginally economic and some that are at present subeconomic). Sources: refs 93, 94 and G. Willeke (Fraunhofer Institute for Solar Energy Systems), Advantages of reduced semiconductor absorber layer thickness. personal communication. C. Wadia, A. Alivisatos, D. Kammen, Environ.described in the43, 2072 (2009). e plasmonic light-trapping concepts Sci. Technol previous MIT Energy Workshop on |Critical Elements for New Energy Technologies | April 29, 2010 NATURE MATERIALS VOL 9 | MARCH 201 | www.nature.com/ naturematerials 0 Burhan Saifaddin Presentation | ENSC S-175 | August 8, 2011 © 20 1 Macmillan Publishers Limited. All rights reserved 0 9 209
    • 10. Other new plasmonic solar-cell designs In arecent exampleof nanoscaleplasmonicsolar-cell engineering, e previous section has focused on the use of plasmonic scattering an organic photovoltaic light absorber was integrated in the gap and coupling concepts to improve the e ciency of single-junction between the arms of plasmonic antennas arranged in arrays (seeExamples on plasmonic solar-cell planar thin- lm solar cells, but many other cell designs can bene t from the increased light con nement and scattering from metal nanostructures. First of all, plasmonic ‘tandem’ geometries may be made, in which semiconductors with di erent bandgaps are Fig. 6c)83. Other examples of nanoscale antennas are coaxial holes fabricated in a metal lm, which show localized plasmonic modes owing to Fabry–Perot resonances (see Fig. 6d)84–86. S nanostructures, with eld enhancements up to a factor of about uch stacked on top of each other, separated by a metal contact layer with 50, could be used in entirely new solar-cell designs, in which an designs a plasmonic nanostructure that couples di erent spectral bands in the solar spectrum into the corresponding semiconductor layer (see Fig. 6a)79. Coupling sunlight into S PPs could also solve the problem of light absorption in quantum-dot solar cells (see Fig. 6b). inexpensive semi conductor with low minority carrier lifetime is embedded inside the plasmonic cavity. S imilarly, quantum-dot solar cells based on multiple-exciton generation87, or cells with solar upconverters or downconverters based on multiphoton absorption Although such cells o er potentially large bene ts because of the e ects, could bene t from such plasmonic eld concentration. In exibility in engineering the semiconductor bandgap by particle general, eld concentration in plasmonic nanostructures is likely size, e ective light absorption requires thick quantum-dot layers, to be useful in any type of solar cell where light concentration is a b p 3.0 eV Incident SPP Top contact n light p 2.0 eV Quantum-dot n SPP guiding layer active layer p 1 eV .0 n c Metal d Metal Semiconductor P3HT Figure 6 | New plasmonic solar-cell designs. a, Plasmonic tandem solar -cell geometry. Semiconductors with di erent bandgaps are stacked on top Plasmonics for improved photovoltaic devices. of each other, separated by a metal contact layer with a plasmonic nanostructur e that couples di erent spectral bands of the solar spectrum int o the corresponding semiconductor layer. b, Plasmonic quantum-dot solar cell designed for enhanced photoabsorption in ultrathin quantum-dot layers mediated Atwater, Polman, Nat. Mat 2010. by coupling t o SPP modes propagating in the plane of the int erface between Ag and the quantum-dot layer. Semiconductor quantum dots are embedded in a metal/ insulator/ metal SPP waveguide. c, Optical ant enna array made from an axial het erostructure of metal and poly(3-hexylthiophene) (P3HT). Light is concentrated in the nanoscale gap between the two antenna arms, and phot ocurrent is generated in the P3HT semiconductor83. d, Array of coaxial holes
    • 11. Plasmonic light trapping in thin-film Si solar cells• Using Finite difference time domain (FDTD): – Designed an array of Ag-particles in combination with an ITO layer that is equivalent to a standard ITO antireflection coating. – Estimated that 95% of the light is transmitted at angles beyond the critical angle for total internal reflection (14 degrees for a-Si:H/air). In another study (Spinelli et al): vary Refractive index vs and scattering peaks. And dound strong Fano resonance effects that reduce the light incoupling for short wavelengths. P Spinelli et al 2012 J. Opt. 14 Fig. 1. Plasmonic light trapping solar cell design. (a) Schematic cross section of the patterned
    • 12. Future work• Dynamics and coupling between plasmons and excitons.• Applications of Finite difference time domain (FDTD).
    • 13. Light trapping in thin Si solar cells using coupled plasmonic antenna• Scattering and coupled spectra depend on particle, shape and dielectric• Systematically