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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 2 — Jan. 27, 2014
  • pp: 1963–1970
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Maximal light-energy transfer through a dielectric/metal-layered electrode on a photoactive device

Kyoung-Ho Kim and Q-Han Park  »View Author Affiliations


Optics Express, Vol. 22, Issue 2, pp. 1963-1970 (2014)
http://dx.doi.org/10.1364/OE.22.001963


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Abstract

We report the fabrication of an optimized low reflective dielectric/metal-layered electrode that provides significant electrical conductivity and light transparency in the near-infrared wavelength regime. By making the metal film thickness thick enough and choosing a proper dielectric layer with a certain thickness, we show that our suggested electrode significantly reduces the light reflection while preserving high electrical conductivity. We demonstrate our optimized electrodes present a highly conductive surface with a sheet resistance of 5.2 Ω/sq and a high light transmittance of near 85% in the near-infrared regime. We also apply our optimized electrode to thin-film organic photovoltaic devices and show the electrode helps in absorbing light energy inside an active layer. We believe that this simple but powerful layered electrode will pave the way for designing transparent electrodes on photoactive devices.

© 2014 Optical Society of America

1. Introduction

Transparent conductive electrodes (TCE) play a crucial role in the operation of photoactive devices such as photodetectors and photovoltaic cells, providing an electrical current path and allowing light transmission into an active layer [1

1. D. S. Hecht, L. Hu, and G. Irvin, “Emerging transparent electrodes based on thin films of carbon nanotubes, graphene, and metallic nanostructures,” Adv. Mater. 23(13), 1482–1513 (2011). [CrossRef] [PubMed]

,2

2. K. Ellmer, “Past achievements and future challenges in the development of optically transparent electrodes,” Nat. Photonics 6(12), 809–817 (2012). [CrossRef]

]. Recently, photoactive devices that operate in the near-infrared (NIR) regime by utilizing low band-gap polymers [3

3. J. Y. Kim, K. Lee, N. E. Coates, D. Moses, T.-Q. Nguyen, M. Dante, and A. J. Heeger, “Efficient tandem polymer solar cells fabricated by all-solution processing,” Science 317(5835), 222–225 (2007). [CrossRef] [PubMed]

,4

4. O. Inganäs, F. Zhang, K. Tvingstedt, L. M. Andersson, S. Hellström, and M. R. Andersson, “Polymer photovoltaics with alternating copolymer/fullerene blends and novel device architectures,” Adv. Mater. 22(20), E100–E116 (2010). [CrossRef] [PubMed]

] or quantum dots [5

5. S. A. McDonald, G. Konstantatos, S. Zhang, P. W. Cyr, E. J. D. Klem, L. Levina, and E. H. Sargent, “Solution-processed PbS quantum dot infrared photodetectors and photovoltaics,” Nat. Mater. 4(2), 138–142 (2005). [CrossRef] [PubMed]

,6

6. T. Rauch, M. Böberl, S. F. Tedde, J. Fürst, M. V. Kovalenko, G. Hesser, U. Lemmer, W. Heiss, and O. Hayden, “Near-infrared imaging with quantum-dot-sensitized organic photodiodes,” Nat. Photonics 3(6), 332–336 (2009). [CrossRef]

] have been suggested for photovoltaic devices and infrared imaging sensors. Consequently, demand for highly conductive, transparent, and flexible TCEs in the NIR regime is increasing. To achieve such electrodes on photoactive devices, dielectric-coated thin noble metal film electrodes have been introduced in the visible light wavelengths range [7

7. C. Guillén and J. Herrero, “TCO/metal/TCO structures for energy and flexible electronics,” Thin Solid Films 520(1), 1–17 (2011). [CrossRef]

10

10. K.-H. Kim and Q.-H. Park, “Perfect anti-reflection from first principles,” Sci. Rep. 3, 1062 (2013). [CrossRef] [PubMed]

]. These electrodes utilize thin noble metal films as a highly conductive surface, and dielectric coatings are applied as an optical admittance matching layers for reducing light reflection from the surface. Symmetric transparent conductive oxide (TCO) coatings on both sides of metal films, called TCO/metal/TCO [oxide/metal/oxide (OMO)] structures, reduce light reflection from the metal surface by utilizing an optical tunneling effect [7

7. C. Guillén and J. Herrero, “TCO/metal/TCO structures for energy and flexible electronics,” Thin Solid Films 520(1), 1–17 (2011). [CrossRef]

,11

11. L. Zhou, W. Wen, C. Chan, and P. Sheng, “Electromagnetic-wave tunneling through negative-permittivity media with high magnetic fields,” Phys. Rev. Lett. 94(24), 243905 (2005). [CrossRef]

]. A dielectric coating on a single side of a metal film (dielectric/metal) also sufficiently reduces light reflection from the metal surface by matching optical admittance on the dielectric surface [8

8. M. V. Schneider, “Schottky barrier photodiodes with antireflection coating,” Bell Syst. Tech. J. 45(9), 1611–1638 (1966). [CrossRef]

10

10. K.-H. Kim and Q.-H. Park, “Perfect anti-reflection from first principles,” Sci. Rep. 3, 1062 (2013). [CrossRef] [PubMed]

]. On both types of dielectric-coated metal electrodes, the thicknesses of the dielectric layers are on the order of tens of nanometers and the thickness of the metal film usually ranges from 10 to 15 nm. Such dielectric-coated metal electrodes show sheet resistance on the order of a few ohms per square and they allow a high light transmittance of more than 90% in the visible light regime. However, in the NIR wavelength regime, these dielectric-coated metal electrodes show the poor electrode performance due to high electrical resistivity while preserving such a high light transmittance. In the case of OMO structures, the thicknesses of the TCO layers are increased in order to meet high transmission requirements because the wavelength of the illuminating light is longer [12

12. X. Liu, X. Cai, J. Mao, and C. Jin, “ZnS/Ag/ZnS nano-multilayer films for transparent electrodes in flat display application,” Appl. Surf. Sci. 183(1-2), 103–110 (2001). [CrossRef]

]. The increase in thickness also increases the contact resistance between the metal electrode and the active layer, which suppresses the entire performance of the photo-active devices [13

13. R. Steim, F. R. Kogler, and C. J. Brabec, “Interface materials for organic solar cells,” J. Mater. Chem. 20(13), 2499–2512 (2010). [CrossRef]

]. For the case of dielectric/metal electrodes, the thickness of the noble metal film layer should be thinner than 7 nm in order to simultaneously meet the need for zero-reflection conditions and high transmission in the NIR regime [8

8. M. V. Schneider, “Schottky barrier photodiodes with antireflection coating,” Bell Syst. Tech. J. 45(9), 1611–1638 (1966). [CrossRef]

,9

9. H. J. Hovel, “Transparency of thin metal films on semiconductor substrates,” J. Appl. Phys. 47(11), 4968–4970 (1976). [CrossRef]

]. However, such thin noble metal films do not form a uniform surface but they form discontinuous isolated surface structures, which causes significant light absorption and high electrical resistivity [14

14. X. Wang, K. P. Chen, M. Zhao, and D. D. Nolte, “Refractive index and dielectric constant transition of ultra-thin gold from cluster to films,” Opt. Express 18(24), 24859–24867 (2010). [CrossRef] [PubMed]

,15

15. J. Siegel, O. Lyutakov, V. Rybka, Z. Kolská, and V. Svorčík, “Properties of gold nanostructures sputtered on glass,” Nanoscale Res. Lett. 6(1), 96 (2011). [CrossRef] [PubMed]

]. Obtaining a balance between optical transparency and electrical conductivity using a systematic optimization method is still lacking in the NIR wavelength regime.

In this letter, we report the fabrication of optimized dielectric/metal-layered electrodes in the NIR wavelength regime that provide highly conductive and transparent surface on the photoactive devices. We fixed the thickness of the noble metal film to form a uniform metal film surface, and we carefully chose the dielectric materials and thickness of the dielectric layer in order to maximize light transmission. To demonstrate our proposed electrode, we optimized and fabricated a ZnS/Au electrode on Si substrate. From the experimental measurements, we demonstrated that our optimized electrodes present a highly conductive surface with a sheet resistance of 5.2 Ω/sq and a high light transmittance of near 85% in the NIR regime. We also analyzed the feasibility of using ZnS/Au electrodes as TCEs by observing the figure of merit (FOM). In addition, we applied the optimized dielectric/metal electrodes to thin-film organic photovoltaic (OPV) devices and show our proposed electrode enhances light absorption inside the active layer of OPV devices.

2. Maximal light transfer through ZnS/Au-layered electrode

Consider light illuminated normally onto a ZnS/Au-layered structure on a Si substrate, as illustrated in Fig. 1(a)
Fig. 1 a) The schematic diagram of the low reflective dielectric/metal electrode composed of ZnS and Gold on a Si substrate. The light illuminated from outside of device and transmitted into the Si substrate. b) The picture of fabricated electrodes on a Si substrate. The electrode structures are composed of ZnS 45 nm/Au 15 nm/Ti 1 nm/Si (A), ZnS 55 nm/Au 15 nm/Ti 1 nm/Si (B), ZnS 65 nm/Au 15 nm/Ti 1 nm/Si (C), Si (D), and Au 15 nm/Ti 1 nm/Si (E).
. In order to maximize the transfer of light energy into the substrate, reducing light reflection by optical admittance matching is essential [10

10. K.-H. Kim and Q.-H. Park, “Perfect anti-reflection from first principles,” Sci. Rep. 3, 1062 (2013). [CrossRef] [PubMed]

]. It was reported that a ZnS 55 nm/Au 10 nm layered coating on a Si substrate met optical admittance matching conditions at a wavelength of 633 nm [8

8. M. V. Schneider, “Schottky barrier photodiodes with antireflection coating,” Bell Syst. Tech. J. 45(9), 1611–1638 (1966). [CrossRef]

]. However, the optical admittance matching conditions used in that study are not practical in the NIR regime because the matching conditions require an extremely thin metal film layer when the wavelength is longer than 633 nm. To meet admittance matching conditions in the NIR wavelength range, the thickness of the gold film should be less than 7 nm. However, such an extremely thin gold film forms a discontinuous surface morphology, which causes poor electrical performance and high light absorption. To achieve a balance between electrical conductivity and optical transmission in the NIR regime, we optimized the thickness of the ZnS layer, which permits maximal light energy transfer into the Si substrate for a fixed gold layer thickness.

The transmittance of incident light through a multilayer system has a complicated analytic expression in terms of material and structural parameters of a multilayer. In order to facilitate the optimization procedure, we express the transmittance utilizing the optical admittance such that
T=4ni2nd2Y0|(ndYmIind2Y0iniYmR)sin(k0ndtd)+(ndniY0+ndYmR+iniYmI)cos(k0ndtd)|2
(1)
where ni and nd are refractive indices of incident medium and dielectric layer, respectively, k0 is the wavenumber in vacuum, Y0 is the optical admittance in vacuum, YmR and YmI are the real and imaginary parts of the optical admittance (Ym = YmR + iYmI) at the dielectric/metal interface. The optical admittance Ym, as the ratio of tangential magnetic field (Hd) and electric field (Ed) at the boundary of dielectric and metal layers, can be obtained from the transfer matrix relation [16

16. H. A. Macleod, Thin-Film Optical Filters, 4th ed. (Taylor and Francis, 2010).

]
(EdHd)=l=1N1(cosϕlinl1sinϕlinlsinϕlcosϕl)(αnsY0α)
(2)
where nl, ϕl = nlk0tl, and tl are the refractive index, optical path length and thickness of the l-th layer, respectively, N is the total number of layers of multilayer system, ns is the refractive index of the substrate and α is an arbitrary constant which does not appear in the optical admittance. In our case as shown in Fig. 1(a), ns, n1 and n2 are refractive indices of the Si substrate, Ti layer and gold layer respectively, and the number of layer (N) is 3. Finally, by minimizing the denominator of transmittance in Eq. (2), the thickness of the ZnS layer (td) that maximizes the light energy transfer for a given wavelength is expressed by
td=λ04πnd[tan1(2ndY0YmInd2Y02YmR2YmI2)+sπ],s=1,3,5...
(3)
where λ0 is the wavelength of incident light and s is an odd-numbered positive integer. From now on, we fix s to 1 for optimized electrodes to possess minimum thickness.

3. Experimental setup and results

For a 15-nm-thick gold film on a Si substrate, as shown in Fig. 1(a), the desired thickness of ZnS layer needed to achieve maximal light transmission at wavelengths of 600, 700, and 800 nm was determined to be 45, 55, and 65 nm, respectively, from Eq. (3). In order to verify our proposed electrodes, we deposited ZnS (45, 55, 65 nm)/Au (15 nm)/Ti (1nm)-layered electrode on a Si substrate. We used a lightly doped (1–30 Ω∙cm) p-type Si wafer. The Si wafer was cleaned with a 1:6 buffered oxide etch (BOE) solution for 1 min to remove the native oxide layer on the Si substrate, followed by rinsing in deionized (DI) water for 3 min and blowing with dry N2. To increase adhesiveness, we introduced a Ti layer between the Au layer and the Si substrate as an adhesion layer, but we limited the thickness to less than 1 nm to avoid large light absorption. We deposited 1 nm thick Ti and 15 nm Au on the cleaned Si wafer by electron-beam (e-beam) evaporation at a vacuum pressure below 10−6 Torr without releasing vacuum at a deposition rate of 0.05 nm s−1 for Ti and 0.1 nm s−1 for Au. After Au deposition, the Au 15 nm/Ti 1 nm /Si wafer was evacuated from the metal deposition chamber in order to coat it with ZnS in another chamber. ZnS was deposited to thicknesses of 45, 55, and 65 nm by e-beam evaporation at a deposition rate of 0.2 nm s−1.

Figure 1(b) depicts the fabricated ZnS/Au electrodes on the Si substrate: ZnS 45 nm/Au 15 nm (A), ZnS 55 nm/Au 15 nm (B), and ZnS 65 nm/Au 15 nm (C). For a comparison, we also fabricated a 15-nm-thick Au film electrode on a Si substrate without a ZnS coating (E). We measured the sheet resistance of the gold electrodes by the four-point probe method and the value was 5.2 Ω/sq. Figure 1(b) clearly shows that the ZnS-coated electrodes show substantial reduction of light reflection as compared to the electrode without a ZnS coating (E).

4. TCEs on thin-film organic photovoltaic devices

We further applied our optimized electrodes to thin-film organic photovoltaic (OPV) devices with a back reflector in visible light wavelengths. As an example, we utilized OPV [18

18. G. Dennler, K. Forberich, M. C. Scharber, C. J. Brabec, I. Tomiš, K. Hingerl, and T. Fromherz, “Angle dependence of external and internal quantum efficiencies in bulk-heterojunction organic solar cells,” J. Appl. Phys. 102(5), 054516 (2007). [CrossRef]

,19

19. J.-F. Salinas, H.-L. Yip, C.-C. Chueh, C.-Z. Li, J.-L. Maldonado, and A. K.-Y. Jen, “Optical design of transparent thin metal electrodes to enhance in-coupling and trapping of light in flexible polymer solar cells,” Adv. Mater. 24(47), 6362–6367 (2012). [CrossRef] [PubMed]

] devices composed of glass/TCE/poly(3,4-ethylenedioxthiophene):poly(styrenesulfonate) (PEDOT:PSS) 10 nm/poly(3-hexylthiophene):1-(3-methoxycarbonyl) propyl-1-phenyl(6,6)C61 (P3HT:PCBM) 90 nm/Ag 200 nm, in which light comes from the glass side, as shown in Fig. 4
Fig. 4 The schematic diagram of analyzed OPV structures and calculated light absorbance spectra in P3HT:PCBM (active layer) as a function of the thickness of the active layer. The used TCEs are: a) ITO 350 nm (ITO350), b) Ag 15 nm (Ag15), and c) TeO2 30 nm/Ag 15 nm (TeO230/Ag15). The maximum absorbance is achieved at a thickness of P3HT:PCBM of 90 nm (white dashed line). d) The comparison of absorbance spectra by using different TCEs. e) The calculated short-circuit current density as a function of thickness of P3HT:PCBM.
. We designed our transparent conductive electrode composed of a 30-nm-thick TeO2 layer and a 15-nm-thick Ag layer as depicted in Fig. 4(c). We determined the thickness of the TeO2 layer from Eq. (3), which maximizes light transmission into the active layer at a wavelength of 460 nm which is close to the absorption peak of P3HT:PCBM. We used silver and TeO2 instead of gold and ZnS in order to avoid unnecessary light absorption inside the TCE structure at wavelengths ranging from 300 to 600 nm. For a comparison, two different electrodes consisting of ITO 350 nm (ITO350) and Ag 15 nm (Ag15) were chosen as the TCEs. All three electrodes had the same sheet resistance of 5.4 Ω/sq [20

20. D. B. Fraser and H. D. Cook, “Highly conductive, transparent films of sputtered In[sub 2−x]Sn[sub x]O[sub 3−y],” J. Electrochem. Soc. 119(10), 1368–1374 (1972). [CrossRef]

, 21

21. B. O’Connor, C. Haughn, K.-H. An, K. P. Pipe, and M. Shtein, “Transparent and conductive electrodes based on unpatterned, thin metal films,” Appl. Phys. Lett. 93(22), 223304 (2008). [CrossRef]

]. Figures 4(a)4(c) show the respective absorption spectra as a function of the thickness of the active layer for the three different electrodes. From the absorption spectra, we chose the P3HT:PCBM thickness of 90 nm (white dashed line) with maximum absorption.

Figure 4(d) shows the absorption spectra inside the 90-nm-thick P3HT:PCBM utilizing ITO350, Ag15, and TeO230/Ag15 electrodes as TCEs. The light absorbance spectra of the active layer are distinctive due to differences in the light transmission properties. Even though ITO is a transparent material, ITO is not helpful in reducing light reflections from the OPV devices; as a result, the light energy transfer into the active layer decreases. The silver-only electrode shows significant absorption enhancement near the wavelength of 600 nm (blue arrow) due to a strong internal cavity mode between the back reflector and the translucent 15-nm-thick silver electrode. However, the strong reflections from the surface of the translucent silver electrode decrease light transmission into the active layer needed for light absorption inside the P3HT:PCBM layer for wavelengths shorter than 600 nm. In contrast to the ITO and the silver electrode without the TeO2 layer, our proposed electrode (TeO230/Ag15) shows substantial enhancement of light absorption for a broad spectral range from 400 to 650 nm. This enhanced light absorption in P3HT:PCBM substantially improves the short-circuit current density (Jsc) as shown in Fig. 4(e). Note that a further increase in the thickness of the silver of the TeO2/Ag electrode is possible. The red dashed line in Fig. 4(e) is Jsc of the OPV devices when TeO2 30 nm/Ag 18 nm (TeO230/Ag18) is applied, and it shows only a small deviation from Jsc of the TeO230/Ag15 electrode. The sheet resistance of Ag 18 nm is 3.8 Ω/sq [21

21. B. O’Connor, C. Haughn, K.-H. An, K. P. Pipe, and M. Shtein, “Transparent and conductive electrodes based on unpatterned, thin metal films,” Appl. Phys. Lett. 93(22), 223304 (2008). [CrossRef]

], which indicates approximately 1.5 times higher conductance than that of the Ag 15 nm electrode. For large-area photovoltaic devices, reduction of the sheet resistance without affecting light absorption inside the active layer is crucial for lowering electrical resistive heat energy loss. The results indicate that our optimized electrodes could be a possible solution for such applications.

5. Conclusion

In this paper, we presented an optimized low-reflective dielectric/metal electrode that provides significant electrical conductivity and light transparency in the NIR regime. We demonstrated experimentally our proposed electrode with a ZnS/Au layer on a Si substrate and showed that this layered electrode significantly reduced the light reflection while preserving low sheet resistance. Furthermore, we applied our optimization method to thin-film OPV devices and showed that the optimized electrode is a candidate for TCEs of large-area photovoltaic devices. We believe that this simple but powerful layered electrode will pave the way for designing transparent electrodes on photo-active devices.

Acknowledgments

This work was supported by the National Research Foundation of Korea (NRF) grant funded by Korea government (MSIP) (N0. 2009-0092831) and Nano-material Technology Development Program (No. 2009-0082665, 2011-0020205).

References and links

1.

D. S. Hecht, L. Hu, and G. Irvin, “Emerging transparent electrodes based on thin films of carbon nanotubes, graphene, and metallic nanostructures,” Adv. Mater. 23(13), 1482–1513 (2011). [CrossRef] [PubMed]

2.

K. Ellmer, “Past achievements and future challenges in the development of optically transparent electrodes,” Nat. Photonics 6(12), 809–817 (2012). [CrossRef]

3.

J. Y. Kim, K. Lee, N. E. Coates, D. Moses, T.-Q. Nguyen, M. Dante, and A. J. Heeger, “Efficient tandem polymer solar cells fabricated by all-solution processing,” Science 317(5835), 222–225 (2007). [CrossRef] [PubMed]

4.

O. Inganäs, F. Zhang, K. Tvingstedt, L. M. Andersson, S. Hellström, and M. R. Andersson, “Polymer photovoltaics with alternating copolymer/fullerene blends and novel device architectures,” Adv. Mater. 22(20), E100–E116 (2010). [CrossRef] [PubMed]

5.

S. A. McDonald, G. Konstantatos, S. Zhang, P. W. Cyr, E. J. D. Klem, L. Levina, and E. H. Sargent, “Solution-processed PbS quantum dot infrared photodetectors and photovoltaics,” Nat. Mater. 4(2), 138–142 (2005). [CrossRef] [PubMed]

6.

T. Rauch, M. Böberl, S. F. Tedde, J. Fürst, M. V. Kovalenko, G. Hesser, U. Lemmer, W. Heiss, and O. Hayden, “Near-infrared imaging with quantum-dot-sensitized organic photodiodes,” Nat. Photonics 3(6), 332–336 (2009). [CrossRef]

7.

C. Guillén and J. Herrero, “TCO/metal/TCO structures for energy and flexible electronics,” Thin Solid Films 520(1), 1–17 (2011). [CrossRef]

8.

M. V. Schneider, “Schottky barrier photodiodes with antireflection coating,” Bell Syst. Tech. J. 45(9), 1611–1638 (1966). [CrossRef]

9.

H. J. Hovel, “Transparency of thin metal films on semiconductor substrates,” J. Appl. Phys. 47(11), 4968–4970 (1976). [CrossRef]

10.

K.-H. Kim and Q.-H. Park, “Perfect anti-reflection from first principles,” Sci. Rep. 3, 1062 (2013). [CrossRef] [PubMed]

11.

L. Zhou, W. Wen, C. Chan, and P. Sheng, “Electromagnetic-wave tunneling through negative-permittivity media with high magnetic fields,” Phys. Rev. Lett. 94(24), 243905 (2005). [CrossRef]

12.

X. Liu, X. Cai, J. Mao, and C. Jin, “ZnS/Ag/ZnS nano-multilayer films for transparent electrodes in flat display application,” Appl. Surf. Sci. 183(1-2), 103–110 (2001). [CrossRef]

13.

R. Steim, F. R. Kogler, and C. J. Brabec, “Interface materials for organic solar cells,” J. Mater. Chem. 20(13), 2499–2512 (2010). [CrossRef]

14.

X. Wang, K. P. Chen, M. Zhao, and D. D. Nolte, “Refractive index and dielectric constant transition of ultra-thin gold from cluster to films,” Opt. Express 18(24), 24859–24867 (2010). [CrossRef] [PubMed]

15.

J. Siegel, O. Lyutakov, V. Rybka, Z. Kolská, and V. Svorčík, “Properties of gold nanostructures sputtered on glass,” Nanoscale Res. Lett. 6(1), 96 (2011). [CrossRef] [PubMed]

16.

H. A. Macleod, Thin-Film Optical Filters, 4th ed. (Taylor and Francis, 2010).

17.

G. Haacke, “New figure of merit for transparent conductors,” J. Appl. Phys. 47(9), 4086–4089 (1976). [CrossRef]

18.

G. Dennler, K. Forberich, M. C. Scharber, C. J. Brabec, I. Tomiš, K. Hingerl, and T. Fromherz, “Angle dependence of external and internal quantum efficiencies in bulk-heterojunction organic solar cells,” J. Appl. Phys. 102(5), 054516 (2007). [CrossRef]

19.

J.-F. Salinas, H.-L. Yip, C.-C. Chueh, C.-Z. Li, J.-L. Maldonado, and A. K.-Y. Jen, “Optical design of transparent thin metal electrodes to enhance in-coupling and trapping of light in flexible polymer solar cells,” Adv. Mater. 24(47), 6362–6367 (2012). [CrossRef] [PubMed]

20.

D. B. Fraser and H. D. Cook, “Highly conductive, transparent films of sputtered In[sub 2−x]Sn[sub x]O[sub 3−y],” J. Electrochem. Soc. 119(10), 1368–1374 (1972). [CrossRef]

21.

B. O’Connor, C. Haughn, K.-H. An, K. P. Pipe, and M. Shtein, “Transparent and conductive electrodes based on unpatterned, thin metal films,” Appl. Phys. Lett. 93(22), 223304 (2008). [CrossRef]

OCIS Codes
(310.0310) Thin films : Thin films
(310.4165) Thin films : Multilayer design
(310.6845) Thin films : Thin film devices and applications
(310.7005) Thin films : Transparent conductive coatings

ToC Category:
Thin Films

History
Original Manuscript: November 25, 2013
Revised Manuscript: December 22, 2013
Manuscript Accepted: December 23, 2013
Published: January 23, 2014

Citation
Kyoung-Ho Kim and Q-Han Park, "Maximal light-energy transfer through a dielectric/metal-layered electrode on a photoactive device," Opt. Express 22, 1963-1970 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-2-1963


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References

  1. D. S. Hecht, L. Hu, G. Irvin, “Emerging transparent electrodes based on thin films of carbon nanotubes, graphene, and metallic nanostructures,” Adv. Mater. 23(13), 1482–1513 (2011). [CrossRef] [PubMed]
  2. K. Ellmer, “Past achievements and future challenges in the development of optically transparent electrodes,” Nat. Photonics 6(12), 809–817 (2012). [CrossRef]
  3. J. Y. Kim, K. Lee, N. E. Coates, D. Moses, T.-Q. Nguyen, M. Dante, A. J. Heeger, “Efficient tandem polymer solar cells fabricated by all-solution processing,” Science 317(5835), 222–225 (2007). [CrossRef] [PubMed]
  4. O. Inganäs, F. Zhang, K. Tvingstedt, L. M. Andersson, S. Hellström, M. R. Andersson, “Polymer photovoltaics with alternating copolymer/fullerene blends and novel device architectures,” Adv. Mater. 22(20), E100–E116 (2010). [CrossRef] [PubMed]
  5. S. A. McDonald, G. Konstantatos, S. Zhang, P. W. Cyr, E. J. D. Klem, L. Levina, E. H. Sargent, “Solution-processed PbS quantum dot infrared photodetectors and photovoltaics,” Nat. Mater. 4(2), 138–142 (2005). [CrossRef] [PubMed]
  6. T. Rauch, M. Böberl, S. F. Tedde, J. Fürst, M. V. Kovalenko, G. Hesser, U. Lemmer, W. Heiss, O. Hayden, “Near-infrared imaging with quantum-dot-sensitized organic photodiodes,” Nat. Photonics 3(6), 332–336 (2009). [CrossRef]
  7. C. Guillén, J. Herrero, “TCO/metal/TCO structures for energy and flexible electronics,” Thin Solid Films 520(1), 1–17 (2011). [CrossRef]
  8. M. V. Schneider, “Schottky barrier photodiodes with antireflection coating,” Bell Syst. Tech. J. 45(9), 1611–1638 (1966). [CrossRef]
  9. H. J. Hovel, “Transparency of thin metal films on semiconductor substrates,” J. Appl. Phys. 47(11), 4968–4970 (1976). [CrossRef]
  10. K.-H. Kim, Q.-H. Park, “Perfect anti-reflection from first principles,” Sci. Rep. 3, 1062 (2013). [CrossRef] [PubMed]
  11. L. Zhou, W. Wen, C. Chan, P. Sheng, “Electromagnetic-wave tunneling through negative-permittivity media with high magnetic fields,” Phys. Rev. Lett. 94(24), 243905 (2005). [CrossRef]
  12. X. Liu, X. Cai, J. Mao, C. Jin, “ZnS/Ag/ZnS nano-multilayer films for transparent electrodes in flat display application,” Appl. Surf. Sci. 183(1-2), 103–110 (2001). [CrossRef]
  13. R. Steim, F. R. Kogler, C. J. Brabec, “Interface materials for organic solar cells,” J. Mater. Chem. 20(13), 2499–2512 (2010). [CrossRef]
  14. X. Wang, K. P. Chen, M. Zhao, D. D. Nolte, “Refractive index and dielectric constant transition of ultra-thin gold from cluster to films,” Opt. Express 18(24), 24859–24867 (2010). [CrossRef] [PubMed]
  15. J. Siegel, O. Lyutakov, V. Rybka, Z. Kolská, V. Svorčík, “Properties of gold nanostructures sputtered on glass,” Nanoscale Res. Lett. 6(1), 96 (2011). [CrossRef] [PubMed]
  16. H. A. Macleod, Thin-Film Optical Filters, 4th ed. (Taylor and Francis, 2010).
  17. G. Haacke, “New figure of merit for transparent conductors,” J. Appl. Phys. 47(9), 4086–4089 (1976). [CrossRef]
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