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Energy Express

  • Editor: Bernard Kippelen
  • Vol. 18, Iss. S4 — Nov. 8, 2010
  • pp: A522–A527
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Simple approach for enhancement of light harvesting efficiency of dye-sensitized solar cells by polymeric mirror

Jun Young Lee, Seungwoo Lee, Jung-Ki Park, Yongseok Jun, Young-Gi Lee, Kwang Man Kim, Jin Ho Yun, and Kuk Young Cho  »View Author Affiliations


Optics Express, Vol. 18, Issue S4, pp. A522-A527 (2010)
http://dx.doi.org/10.1364/OE.18.00A522


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Abstract

A Polymeric mirror from 1D photonic crystal exhibiting full specular reflection is applied on the exterior of the counter electrode of a dye-sensitized solar cells (DSSCs). Reflection of exiting light from the cell allows for the reuse of the light and thereby significantly increases the efficiency of the DSSCs (from 8.07% to 8.85%). Furthermore, it is also found to be effective even with incorporation of an internal scattering layer, which is widely used within a TiO2 anode layer for enhancing light trapping in DSSCs (from 9.17% to 9.53%).

© 2010 OSA

Multilayer polymeric films with an alternating quarter-wavelength thick high refractive index and a low index material can be used to fabricate omnidirectional mirrors [11

11. M. F. Weber, C. A. Stover, L. R. Gilbert, T. J. Nevitt, and A. J. Ouderkirk, “Giant birefringent optics in multilayer polymer mirrors,” Science 287(5462), 2451–2456 (2000). [CrossRef] [PubMed]

,12

12. S. D. Hart, G. R. Maskaly, B. Temelkuran, P. H. Prideaux, J. D. Joannopoulos, and Y. Fink, “External reflection from omnidirectional dielectric mirror fibers,” Science 296(5567), 510–513 (2002). [CrossRef] [PubMed]

]. Reflection of a polymeric mirror follows Eq. (1) and increases with the number of stacked multilayers, resulting in specular reflection.
R=[1(nlow/nhigh)2m1(nlow/nhigh)2m]2
(1)
R, nlow, nhigh, and m in the Eq. (1) represent reflectivity of polymeric mirror, low and high refractive index of stacked material, and number of periods of the stacked layer, respectively. On the other hand, metallic foils such as aluminum film also show specular reflection. However, a polymeric mirror consisting of a distributed Bragg reflector exhibits sharp angular width of the specular peak (constant intensity at the reflection angle equal to the incident angle) [13

13. M. Janecek and W. W. Moses, “Optical reflectance measurements for commonly used reflectors,” IEEE Trans. Nucl. Sci. 55(4), 2432–2437 (2008). [CrossRef]

] and is free from oxidation at the surface. Owing to its superior reflective properties, multilayers fabricated by the continuous multilayer coextrusion process are currently used as highly reflective films in mobile liquid crystalline display (LCD) devices. Since reflection can be classified into specular and diffuse reflection, we selected diffuse reflective polymeric film for comparison in this work. The reflection (total, specular, and diffuse reflection) characteristics of polymeric reflective films are measured using a Cary 600i UV-Vis-NIR spectrometer (Varian) and the results are shown in Fig. 2
Fig. 2 Reflectance spectra of (a) polymeric mirror and (b) white diffuse reflection film in the range of visible wavelength region. Angle of incidence is 7° where normal incidence is set to 0° and the total and diffuse reflectance were measured with detector varying the angle. Specular reflectance is calculated by the difference of total and diffuse reflectance.
. A polymeric mirror (Thickness: 65 μm, VikuitiTM ESR, 3M), and a white diffuse reflective film (RP14, SKC) are used as representative specular and diffuse reflective films, respectively. The two reflective films showed almost the same reflectivity over the visible wavelength region. The polymeric mirror showed very similar values of total reflection and specular reflection, thus illustrating that the reflection is fully specular. In the case of the diffuse reflective film, the total reflection originates mainly from diffuse reflection and a small amount of specular reflection.

It can be easily concluded from the J-V curves that simple attachment of a reflective film at the exterior of the Pt counter electrode increased JSC, while leaving the open circuit voltage, VOC, unaltered. This phenomenon was observed from both of the polymeric mirror and the white diffuse reflective film (Fig. 3(a)). However, specular reflection from the polymeric mirror was more effective in improving JSC compared to diffuse reflective films despite similar total reflection ability. With respect to participation of the reflected light in the increasing light efficiency, the reflected light should reach dye on the titanium particles to generate electrons. It is speculated that slight increase of the reflected light absorbed by the electrolyte (triiodide species) [18

18. A. B. F. Martinson, T. W. Hamann, M. J. Pellin, and J. T. Hupp, “New architectures for dye-sensitized solar cells,” Chemistry 14(15), 4458–4467 (2008). [CrossRef] [PubMed]

] or small portion of light loss through the edge of the cell owing to the change of reflection angle by the the diffuse reflective film is the cause of reduced amount of light reaching the titanium particles compared to that of a polymeric mirror. IPCE spectra also indicate an increase of JSC when a reflective film is applied. The maximum value of IPCE is obtained around the wavelength of 540 nm, which corresponds to maximum absorption for N719. With the reflective film attached to the exterior of the counter electrode, IPCE increased over the range of the visible region.

To investigate the effect of specular reflection on the increase of the light pass in the cell, power conversion efficiency was measured varying the angle of incidence. Polymeric mirror and aluminum foil were used as specular reflectors and the result is illustrated in Fig. 4
Fig. 4 Power coversion efficiency of DSSC with varying angle of the incident light.
. Reference cell exhibiting 6.0% efficiency was used and the similar trend of increasing power conversion efficiency compared to reference cell with 8.07% efficiency was obtained. Interestingly, additional increase of the power conversion efficiency was observed when the incident angle was 20° (normal incident angle is 0°) when the specular reflector was applied onto the reference cell. This optimal trend of power conversion is originated from the competence of increase of the light reflection at the surface of glass anode and increase of the light passway. This two factors oppositely affect power conversion efficiency. The former deteriorate power conversion efficiency. Severe reflection from glass anode after 40° eliminated the effect of specular reflector.

In conclusion, we have suggested a simple but powerful approach of utilizing a reflective film at the exterior of the cell in order to enhance the power conversion efficiency. Specular reflection via multilayer stacking of a polymeric film with alternating refractive indices increased JSC and the resulting η. Broad-band reflection and conformable properties of 1D photonic crystals based on the polymeric mirror can potentially be applied to other solar cell systems and flexible DSSCs where reflection is important.

Acknowledgements

This research is supported by the Converging Research Center Program (no. 20090093657) and Brain Korea project through the National Research Foundation (NRF) funded by the Ministry of Education, Science, and Technology.

References and links

1.

B. O’Regan and M. Grätzel, “A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films,” Nature 353(6346), 737–740 (1991). [CrossRef]

2.

X. Fan, F. Wang, Z. Chu, L. Chen, C. Zhang, and D. Zou, “Conductive mesh based flexible dye-sensitized solar cells,” Appl. Phys. Lett. 90(7), 073501 (2007). [CrossRef]

3.

M. Ikegami, J. Suzuki, K. Teshima, M. Kawaraya, and T. Miyasaka, “Improvement in durability of flexible plastic dye-sensitized solar cell modules,” Sol. Energy Mater. Sol. Cells 93(6-7), 836–839 (2009). [CrossRef]

4.

Y. H. Luo, D. M. Li, and Q. B. Meng, “Towards optimization of materials for dye-sensitized solar cells,” Adv. Mater. 21(45), 4647–4651 (2009). [CrossRef]

5.

Y. Tachibana, K. Hara, K. Sayama, and H. Arakawa, “Quantitative analysis of light-harvesting efficiency and electron-transfer yield in ruthenium-dye-sensitized nanocrystalline TiO2 solar cells,” Chem. Mater. 14(6), 2527–2535 (2002). [CrossRef]

6.

K. A. Arpin, A. Mihi, H. T. Johnson, A. J. Baca, J. A. Rogers, J. A. Lewis, and P. V. Braun, “Multidimensional architectures for functional optical devices,” Adv. Mater. 22(10), 1084–1101 (2010). [CrossRef] [PubMed]

7.

A. Mihi, F. J. López-Alcaraz, and H. Miguez, “Full spectrum enhancement of the light harvesting efficiency of dye sensitized solar cells by including colloidal photonic crystal multilayers,” Appl. Phys. Lett. 88(19), 193110 (2006). [CrossRef]

8.

S. Colodrero, A. Mihi, L. Häggman, M. Ocaña, G. Boschloo, A. Hagfeldt, and H. Miguez, “Porous one-dimensional photonic crystals improve the power-conversion efficiency of dye-sensitized solar cells,” Adv. Mater. 21(7), 764–770 (2009). [CrossRef]

9.

G. Lozano, S. Colodrero, O. Caulier, M. E. Calvo, and H. Miguez, “Theoretical analysis of the performance of one-dimensional photonic crystal-based dye-sensitized solar cells,” J. Phys. Chem. C 114(8), 3681–3687 (2010). [CrossRef]

10.

Y. Zhang, J. Wang, Y. Zhao, J. Zhai, L. Jiang, Y. Song, and D. Zhu, “Photonic crystal concentrator for efficient output of dye-sensitized solar cells,” J. Mater. Chem. 18(23), 2650–2652 (2008). [CrossRef]

11.

M. F. Weber, C. A. Stover, L. R. Gilbert, T. J. Nevitt, and A. J. Ouderkirk, “Giant birefringent optics in multilayer polymer mirrors,” Science 287(5462), 2451–2456 (2000). [CrossRef] [PubMed]

12.

S. D. Hart, G. R. Maskaly, B. Temelkuran, P. H. Prideaux, J. D. Joannopoulos, and Y. Fink, “External reflection from omnidirectional dielectric mirror fibers,” Science 296(5567), 510–513 (2002). [CrossRef] [PubMed]

13.

M. Janecek and W. W. Moses, “Optical reflectance measurements for commonly used reflectors,” IEEE Trans. Nucl. Sci. 55(4), 2432–2437 (2008). [CrossRef]

14.

K. Shin, Y. Jun, J. H. Moon, and J. H. Park, “Observation of positive effects of freestanding scattering film in dye-sensitized solar cells,” ACS Appl Mater Interfaces 2(1), 288–291 (2010). [CrossRef] [PubMed]

15.

J. Y. Lee, B. Bhattacharya, D. W. Kim, and J. K. Park, “Poly(ethylene oxide)/poly(dimethylsiloxane) blend solid polymer electrolyte and its dye-sensitized solar cell applications,” J. Phys. Chem. C 112(32), 12576–12582 (2008). [CrossRef]

16.

B. Bhattacharya, J. Y. Lee, J. Geng, H. T. Jung, and J. K. Park, “Effect of cation size on solid polymer electrolyte based dye-sensitized solar cells,” Langmuir 25(5), 3276–3281 (2009). [CrossRef] [PubMed]

17.

Y. Jun, J. H. Son, D. Sohn, and M. G. Kang, “A module of a TiO2 nanocrystalline dye-sensitized solar cell with effective dimensions,” J. Photochem. Photobiol. A 200(2-3), 314–317 (2008). [CrossRef]

18.

A. B. F. Martinson, T. W. Hamann, M. J. Pellin, and J. T. Hupp, “New architectures for dye-sensitized solar cells,” Chemistry 14(15), 4458–4467 (2008). [CrossRef] [PubMed]

OCIS Codes
(160.5470) Materials : Polymers
(350.6050) Other areas of optics : Solar energy

ToC Category:
Photovoltaics

History
Original Manuscript: August 16, 2010
Revised Manuscript: September 14, 2010
Manuscript Accepted: September 14, 2010
Published: September 24, 2010

Citation
Jun Young Lee, Seungwoo Lee, Jung-Ki Park, Yongseok Jun, Young-Gi Lee, Kwang Man Kim, Jin Ho Yun, and Kuk Young Cho, "Simple approach for enhancement of light harvesting efficiency of dye-sensitized solar cells by polymeric mirror," Opt. Express 18, A522-A527 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-S4-A522


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References

  1. B. O’Regan and M. Grätzel, “A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films,” Nature 353(6346), 737–740 (1991). [CrossRef]
  2. X. Fan, F. Wang, Z. Chu, L. Chen, C. Zhang, and D. Zou, “Conductive mesh based flexible dye-sensitized solar cells,” Appl. Phys. Lett. 90(7), 073501 (2007). [CrossRef]
  3. M. Ikegami, J. Suzuki, K. Teshima, M. Kawaraya, and T. Miyasaka, “Improvement in durability of flexible plastic dye-sensitized solar cell modules,” Sol. Energy Mater. Sol. Cells 93(6-7), 836–839 (2009). [CrossRef]
  4. Y. H. Luo, D. M. Li, and Q. B. Meng, “Towards optimization of materials for dye-sensitized solar cells,” Adv. Mater. 21(45), 4647–4651 (2009). [CrossRef]
  5. Y. Tachibana, K. Hara, K. Sayama, and H. Arakawa, “Quantitative analysis of light-harvesting efficiency and electron-transfer yield in ruthenium-dye-sensitized nanocrystalline TiO2 solar cells,” Chem. Mater. 14(6), 2527–2535 (2002). [CrossRef]
  6. K. A. Arpin, A. Mihi, H. T. Johnson, A. J. Baca, J. A. Rogers, J. A. Lewis, and P. V. Braun, “Multidimensional architectures for functional optical devices,” Adv. Mater. 22(10), 1084–1101 (2010). [CrossRef] [PubMed]
  7. A. Mihi, F. J. López-Alcaraz, and H. Miguez, “Full spectrum enhancement of the light harvesting efficiency of dye sensitized solar cells by including colloidal photonic crystal multilayers,” Appl. Phys. Lett. 88(19), 193110 (2006). [CrossRef]
  8. S. Colodrero, A. Mihi, L. Häggman, M. Ocaña, G. Boschloo, A. Hagfeldt, and H. Miguez, “Porous one-dimensional photonic crystals improve the power-conversion efficiency of dye-sensitized solar cells,” Adv. Mater. 21(7), 764–770 (2009). [CrossRef]
  9. G. Lozano, S. Colodrero, O. Caulier, M. E. Calvo, and H. Miguez, “Theoretical analysis of the performance of one-dimensional photonic crystal-based dye-sensitized solar cells,” J. Phys. Chem. C 114(8), 3681–3687 (2010). [CrossRef]
  10. Y. Zhang, J. Wang, Y. Zhao, J. Zhai, L. Jiang, Y. Song, and D. Zhu, “Photonic crystal concentrator for efficient output of dye-sensitized solar cells,” J. Mater. Chem. 18(23), 2650–2652 (2008). [CrossRef]
  11. M. F. Weber, C. A. Stover, L. R. Gilbert, T. J. Nevitt, and A. J. Ouderkirk, “Giant birefringent optics in multilayer polymer mirrors,” Science 287(5462), 2451–2456 (2000). [CrossRef] [PubMed]
  12. S. D. Hart, G. R. Maskaly, B. Temelkuran, P. H. Prideaux, J. D. Joannopoulos, and Y. Fink, “External reflection from omnidirectional dielectric mirror fibers,” Science 296(5567), 510–513 (2002). [CrossRef] [PubMed]
  13. M. Janecek and W. W. Moses, “Optical reflectance measurements for commonly used reflectors,” IEEE Trans. Nucl. Sci. 55(4), 2432–2437 (2008). [CrossRef]
  14. K. Shin, Y. Jun, J. H. Moon, and J. H. Park, “Observation of positive effects of freestanding scattering film in dye-sensitized solar cells,” ACS Appl Mater Interfaces 2(1), 288–291 (2010). [CrossRef] [PubMed]
  15. J. Y. Lee, B. Bhattacharya, D. W. Kim, and J. K. Park, “Poly(ethylene oxide)/poly(dimethylsiloxane) blend solid polymer electrolyte and its dye-sensitized solar cell applications,” J. Phys. Chem. C 112(32), 12576–12582 (2008). [CrossRef]
  16. B. Bhattacharya, J. Y. Lee, J. Geng, H. T. Jung, and J. K. Park, “Effect of cation size on solid polymer electrolyte based dye-sensitized solar cells,” Langmuir 25(5), 3276–3281 (2009). [CrossRef] [PubMed]
  17. Y. Jun, J. H. Son, D. Sohn, and M. G. Kang, “A module of a TiO2 nanocrystalline dye-sensitized solar cell with effective dimensions,” J. Photochem. Photobiol. A 200(2-3), 314–317 (2008). [CrossRef]
  18. A. B. F. Martinson, T. W. Hamann, M. J. Pellin, and J. T. Hupp, “New architectures for dye-sensitized solar cells,” Chemistry 14(15), 4458–4467 (2008). [CrossRef] [PubMed]

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