We review the use of self-assembled, vertically oriented one-dimensional (1D) titania nanowire and nanotube geometries in several third-generation excitonic solar cell designs including those based upon bulk heterojunction, ordered heterojunction, F？rster resonance energy transfer (FRET), and liquid-junction dye-sensitized solar cells (DSSCs). 1. Introduction Third-generation photovoltaics encompass a variety of designs including liquid-based dye-sensitized (Gr？tzel) solar cells, solid-state bulk heterojunction solar cells [1–6], ordered heterojunction solar cells [7, 8], F？rster resonance energy transfer- (FRET-) based solar cells [9–14], and organic solar cells [15, 16]. Liquid-based dye-sensitized solar cells (DSSCs) utilizing for a photoanode a dye-coated layer of TiO2 nanoparticles have reached efficiencies of over 11% [17], but there are concerns with respect to manufacturing photovoltaic panels with a liquid redox electrolyte. Solid-state organic solar cells are easy to handle and manufacture, and have demonstrated efficiencies ranging from 2 to 8.13% [18–20]. Other 3rd generation photovoltaic designs include plasmonic resonance devices [21], quantum dot and, hopefully, multiple exciton devices [22, 23]. Various nanostructures have been used as a means of energy conversion enhancement in 3rd generation solar cells. These structures can be classified into four types: (a) Nanocomposite (3-dimensional), (b) quantum well (2-dimensional), (c) nanowire and nanotubes (1-dimensional, 1D), and (d) nanoparticles (0-dimensional). Our interest in this paper is the photovoltaic application of self-assembled TiO2-based 1D nanostructures. Self-organized TiO2 nanowires/nanotubes arrays [24, 25] vertically oriented on a transparent conducting oxide (TCO) substrate offer numerous benefits such as large surface area for dye sensitization resulting in enhanced light harvesting, easy transfer of electrons injected from photon excited dye, vectorial (directed) charge transport to the electrical contact, and a readily assessable space for intercalation of the redox electrolyte or p-type semiconductor. However, while self-assembled vertically oriented 1D titania nanoarchitectured films offer great potential for enhancing 3rd generation photovoltaic efficiencies to date, such films have not yet been achieved. There is, to date, something always lacking in such fields, be it poor crystallinity of the electron transporting backbone which results in poor charge transport, damage to the transparent conductive oxide coating which increases the series resistance and/or reduces
References
[1]
O. K. Varghese and C. A. Grimes, “Appropriate strategies for determining the photoconversion efficiency of water photoelectrolysis cells: a review with examples using titania nanotube array photoanodes,” Solar Energy Materials and Solar Cells, vol. 92, no. 4, pp. 374–384, 2008.
[2]
Z. Li, K. Shankar, G. K. Mor, et al., “Functionalized pentacenes for dye-sensitized solar cells,” Journal of Photonics for Energy, vol. 1, Article ID 011106, 2011.
[3]
S.-T. Fei, S.-H. A. Lee, S. M. Pursel et al., “Electrolyte infiltration in phosphazene-based dye-sensitized solar cells,” Journal of Power Sources, vol. 196, no. 11, pp. 5223–5230, 2011.
[4]
J. Bandara, K. Shankar, J. Basham et al., “Integration of TiO2 nanotube arrays into solid-state dye-sensitized solar cells,” EPJ Applied Physics, vol. 53, no. 2, Article ID 20601, 2011.
[5]
Q. Kang, S. H. Liu, L. X. Yang, Q. Y. Cai, and C. A. Grimes, “Fabrication of PbS nanoparticle sensitized TiO2 nanotube arrays and their photoelectrochemical properties,” ACS Applied Materials & Interfaces, vol. 3, pp. 746–749, 2011.
[6]
M. C. Scharber, D. Mühlbacher, M. Koppe et al., “Design rules for donors in bulk-heterojunction solar cells—towards 10 % energy-conversion efficiency,” Advanced Materials, vol. 18, no. 6, pp. 789–794, 2006.
[7]
G. K. Mor, S. Kim, M. Paulose et al., “Visible to near-infrared light harvesting in TiO2 nanotube array-P3HT based heterojunction solar cells,” Nano Letters, vol. 9, no. 12, pp. 4250–4257, 2009.
[8]
M. D. McGehee, “Nanostructured organic-inorganic hybrid solar cells,” MRS Bulletin, vol. 34, no. 2, pp. 95–100, 2009.
[9]
K. Shankar, X. Feng, and C. A. Grimes, “Enhanced harvesting of red photons in nanowire solar cells: evidence of resonance energy transfer,” ACS Nano, vol. 3, no. 4, pp. 788–794, 2009.
[10]
B. E. Hardin, E. T. Hoke, P. B. Armstrong et al., “Increased light harvesting in dye-sensitized solar cells with energy relay dyes,” Nature Photonics, vol. 3, no. 7, pp. 406–411, 2009.
[11]
J. H. Yum, B. E. Hardin, S. J. Moon et al., “Panchromatic response in solid-state dye-sensitized solar cells containing phosphorescent energy relay dyes,” Angewandte Chemie - International Edition, vol. 48, no. 49, pp. 9277–9280, 2009.
[12]
G. K. Mor, J. Basham, M. Paulose et al., “High-efficiency f？rster resonance energy transfer in solid-state dye sensitized solar cells,” Nano Letters, vol. 10, no. 7, pp. 2387–2394, 2010.
[13]
J. I. Basham, G. K. Mor, and C. A. Grimes, “F？rster resonance energy transfer in dye-sensitized solar cells,” ACS Nano, vol. 4, no. 3, pp. 1253–1258, 2010.
[14]
S. Buhbut, S. Itzhakov, E. Tauber et al., “Built-in quantum dot antennas in dye-sensitized solar cells,” ACS Nano, vol. 4, no. 3, pp. 1293–1298, 2010.
[15]
P. Chen, J. H. Yum, F. De Angelis et al., “High open-circuit voltage solid-state dye-sensitized solar cells with organic dye,” Nano Letters, vol. 9, no. 6, pp. 2487–2492, 2009.
[16]
G. K. R. Senadeera, P. V. V. Jayaweera, V. P. S. Perera, and K. Tennakone, “Solid-state dye-sensitized photocell based on pentacene as a hole collector,” Solar Energy Materials and Solar Cells, vol. 73, no. 1, pp. 103–108, 2002.
[17]
B. O'Regan and M. Gr？tzel, “A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films,” Nature, vol. 353, no. 6346, pp. 737–740, 1991.
[18]
S. H. Park, A. Roy, S. Beaupré et al., “Bulk heterojunction solar cells with internal quantum efficiency approaching 100%,” Nature Photonics, vol. 3, no. 5, pp. 297–303, 2009.
[19]
H. Y. Chen, J. Hou, S. Zhang et al., “Polymer solar cells with enhanced open-circuit voltage and efficiency,” Nature Photonics, vol. 3, no. 11, pp. 649–653, 2009.
K. Nakayama, K. Tanabe, and H. A. Atwater, “Plasmonic nanoparticle enhanced light absorption in GaAs solar cells,” Applied Physics Letters, vol. 93, no. 12, Article ID 121904, 2008.
[22]
A. Luque, A. Martí, and A. J. Nozik, “Solar cells based on quantum dots: multiple exciton generation and intermediate bands,” MRS Bulletin, vol. 32, no. 3, pp. 236–241, 2007.
[23]
A. G. Pattantyus-Abraham, I. J. Kramer, A. R. Barkhouse et al., “Depleted-heterojunction colloidal quantum dot solar cells,” ACS Nano, vol. 4, no. 6, pp. 3374–3380, 2010.
[24]
X. Feng, K. Shankar, O. K. Varghese, M. Paulose, T. J. Latempa, and C. A. Grimes, “Vertically aligned single crystal TiO2 nanowire arrays grown directly on transparent conducting oxide coated glass: synthesis details and applications,” Nano Letters, vol. 8, no. 11, pp. 3781–3786, 2008.
[25]
G. K. Mor, K. Shankar, M. Paulose, O. K. Varghese, and C. A. Grimes, “Use of highly-ordered TiO2 nanotube arrays in dye-sensitized solar cells,” Nano Letters, vol. 6, no. 2, pp. 215–218, 2006.
[26]
D. Gong, C. A. Grimes, O. K. Varghese et al., “Titanium oxide nanotube arrays prepared by anodic oxidation,” Journal of Materials Research, vol. 16, no. 12, pp. 3331–3334, 2001.
[27]
M. Paulose, K. Shankar, S. Yoriya et al., “Anodic growth of highly ordered TiO2 nanotube arrays to 134 μm in length,” Journal of Physical Chemistry B, vol. 110, no. 33, pp. 16179–16184, 2006.
[28]
K. Zhu, N. R. Neale, A. Miedaner, and A. J. Frank, “Enhanced charge-collection efficiencies and light scattering in dye-sensitized solar cells using oriented TiO2 nanotubes arrays,” Nano Letters, vol. 7, no. 1, pp. 69–74, 2007.
[29]
J. R. Jennings, A. Ghicov, L. M. Peter, P. Schmuki, and A. B. Walker, “Dye-sensitized solar cells based on oriented TiO2 nanotube arrays: transport, trapping, and transfer of electrons,” Journal of the American Chemical Society, vol. 130, no. 40, pp. 13364–13372, 2008.
[30]
H. E. Prakasam, K. Shankar, M. Paulose, O. K. Varghese, and C. A. Grimes, “A new benchmark for TiO2 nanotube array growth by anodization,” Journal of Physical Chemistry C, vol. 111, no. 20, pp. 7235–7241, 2007.
[31]
S. Yoriya, G. K. Mor, S. Sharma, and C. A. Grimes, “Synthesis of ordered arrays of discrete, partially crystalline titania nanotubes by Ti anodization using diethylene glycol electrolytes,” Journal of Materials Chemistry, vol. 18, no. 28, pp. 3332–3336, 2008.
[32]
S. Yoriya, M. Paulose, O. K. Varghese, G. K. Mor, and C. A. Grimes, “Fabrication of vertically oriented TiO2 nanotube arrays using dimethyl sulfoxide electrolytes,” Journal of Physical Chemistry C, vol. 111, no. 37, pp. 13770–13776, 2007.
[33]
K. Shankar, G. K. Mor, A. Fitzgerald, and C. A. Grimes, “Cation effect on the electrochemical formation of very high aspect ratio TiO2 nanotube arrays in formamide-water mixtures,” Journal of Physical Chemistry C, vol. 111, no. 1, pp. 21–26, 2007.
[34]
K. Shankar, G. K. Mor, H. E. Prakasam et al., “Highly-ordered TiO2 nanotube arrays up to 220 μm in length: use in water photoelectrolysis and dye-sensitized solar cells,” Nanotechnology, vol. 18, no. 6, Article ID 065707, 2007.
[35]
O. K. Varghese, M. Paulose, and C. A. Grimes, “Long vertically aligned titania nanotubes on transparent conducting oxide for highly efficient solar cells,” Nature Nanotechnology, vol. 4, no. 9, pp. 592–597, 2009.
[36]
O. K. Varghese, D. Gong, M. Paulose, C. A. Grimes, and E. C. Dickey, “Crystallization and high-temperature structural stability of titanium oxide nanotube arrays,” Journal of Materials Research, vol. 18, no. 1, pp. 156–165, 2003.
[37]
C. A. Grimes and G. K. Mor, TiO2 Nanotube Arrays Synthesis, Properties, and Applications, Springer, Berlin, Germany, 2009.
[38]
G. K. Mor, K. Shankar, M. Paulose, O. K. Varghese, and C. A. Grimes, “High efficiency double heterojunction polymer photovoltaic cells using highly ordered TiO2 nanotube arrays,” Applied Physics Letters, vol. 91, no. 15, Article ID 152111, 2007.
[39]
S. Günes, H. Neugebauer, and N. S. Sariciftci, “Conjugated polymer-based organic solar cells,” Chemical Reviews, vol. 107, no. 4, pp. 1324–1338, 2007.
[40]
S. A. Jenekhe and X. L. Chen, “Self-assembled aggregates of rod-coil block copolymers and their solubilization and encapsulation of Fullerenes,” Science, vol. 279, no. 5358, pp. 1903–1907, 1998.
[41]
G. Hadziioannou and F. von Hutten, Semiconducting Polymers, Wiley-VCH, Weinheim, Germany, 2000.
[42]
N. S. Sariciftci and S. S. Sun, Organic Photovoltaics, Taylor & Francis, London, UK, 2005.
[43]
A. Tracz, J. K. Jeszka, M. D. Watson, W. Pisula, K. Müllen, and T. Pakula, “Uniaxial alignment of the columnar super-structure of a hexa (alkyl) hexa-peri-hexabenzocoronene on untreated glass by simple solution processing,” Journal of the American Chemical Society, vol. 125, no. 7, pp. 1682–1683, 2003.
[44]
K. M. Coakley and M. D. McGehee, “Photovoltaic cells made from conjugated polymers infiltrated into mesoporous titania,” Applied Physics Letters, vol. 83, no. 16, pp. 3380–3382, 2003.
[45]
K. Shankar, G. K. Mor, M. Paulose, O. K. Varghese, and C. A. Grimes, “Effect of device geometry on the performance of TiO2 nanotube array-organic semiconductor double heterojunction solar cells,” Journal of Non-Crystalline Solids, vol. 354, no. 19–25, pp. 2767–2771, 2008.
[46]
K. Shankar, G. K. Mor, H. E. Prakasam, O. K. Varghese, and C. A. Grimes, “Self-assembled hybrid polymer-TiO2 nanotube array heterojunction solar cells,” Langmuir, vol. 23, no. 24, pp. 12445–12449, 2007.
[47]
D. C. Olson, J. Piris, R. T. Collins, S. E. Shaheen, and D. S. Ginley, “Hybrid photovoltaic devices of polymer and ZnO nanofiber composites,” Thin Solid Films, vol. 496, no. 1, pp. 26–29, 2006.
[48]
J. Y. Kim, S. H. Kim, H. H. Lee et al., “New architecture for high-efficiency polymer photovoltaic cells using solution-based titanium oxide as an optical spacer,” Advanced Materials, vol. 18, no. 5, pp. 572–576, 2006.
[49]
J. Peet, J. Y. Kim, N. E. Coates et al., “Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols,” Nature Materials, vol. 6, no. 7, pp. 497–500, 2007.
[50]
K. M. Coakley, Y. Liu, M. D. McGehee, K. L. Frindell, and G. D. Stucky, “Infiltrating semiconducting polymers into self-assembled mesoporous titania films for photovoltaic applications,” Advanced Functional Materials, vol. 13, no. 4, pp. 301–306, 2003.
[51]
S. Kim, G. K. Mor, M. Paulose, O. K. Varghese, K. Shankar, and C. A. Grimes, “Broad spectrum light harvesting in TiO2 nanotube array hemicyanine dye P3HT hybrid solid-state solar cells,” IEEE Journal on Selected Topics in Quantum Electronics, vol. 16, no. 6, pp. 1573–1580, 2010.
[52]
K. M. Coakley and M. D. McGehee, “Conjugated polymer photovoltaic cells,” Chemistry of Materials, vol. 16, no. 23, pp. 4533–4542, 2004.
[53]
F. Nuesch, J. E. Moser, V. Shklover, and M. Gratzel, “Merocyanine aggregation in mesoporous networks,” Journal of the American Chemical Society, vol. 118, no. 23, pp. 5420–5431, 1996.
[54]
G. K. Mor, O. K. Varghese, M. Paulose, K. Shankar, and C. A. Grimes, “A review on highly ordered, vertically oriented TiO2 nanotube arrays: fabrication, material properties, and solar energy applications,” Solar Energy Materials and Solar Cells, vol. 90, no. 14, pp. 2011–2075, 2006.
[55]
K. M. Coakley, B. S. Srinivasan, J. M. Ziebarth, C. Goh, Y. Liu, and M. D. McGehee, “Enhanced hole mobility in regioregular polythiophene infiltrated in straight nanopores,” Advanced Functional Materials, vol. 15, no. 12, pp. 1927–1932, 2005.
[56]
T. A. Chen, X. Wu, and R. D. Rieke, “Regiocontrolled synthesis of poly(3-alkylthiophenes) mediated by Rieke zinc: their characterization and solid-state properties,” Journal of the American Chemical Society, vol. 117, no. 1, pp. 233–244, 1995.
[57]
W. Ma, C. Yang, X. Gong, K. Lee, and A. J. Heeger, “Thermally stable, efficient polymer solar cells with nanoscale control of the interpenetrating network morphology,” Advanced Functional Materials, vol. 15, no. 10, pp. 1617–1622, 2005.
[58]
T. F？rster, “10th Spiers Memorial Lecture. Transfer mechanisms of electronic excitation,” Discussions of the Faraday Society, vol. 27, pp. 7–17, 1959.
[59]
Y. Liu, M. A. Summers, C. Edder, J. M. J. Fréchet, and M. D. McGehee, “Using resonance energy transfer to improve exciton harvesting in organic-inorganic hybrid photovoltaic cells,” Advanced Materials, vol. 17, no. 24, pp. 2960–2964, 2005.
[60]
C. X. Sheng, M. Tong, S. Singh, and Z. V. Vardeny, “Experimental determination of the charge/neutral branching ratio η in the photoexcitation of π -conjugated polymers by broadband ultrafast spectroscopy,” Physical Review B, vol. 75, no. 8, Article ID 085206, 2007.
[61]
S. R. Scully and M. D. McGehee, “Effects of optical interference and energy transfer on exciton diffusion length measurements in organic semiconductors,” Journal of Applied Physics, vol. 100, no. 3, Article ID 034907, 2006.
[62]
S. R. Scully, P. B. Armstrong, C. Edder, J. M. J. Fréchet, and M. D. McGehee, “Long-range resonant energy transfer for enhanced exciton harvesting for organic solar cells,” Advanced Materials, vol. 19, no. 19, pp. 2961–2966, 2007.
[63]
S. A. Haque, Y. Tachibana, R. L. Willis et al., “Parameters influencing charge recombination kinetics in dye-sensitized nanocrystalline titanium dioxide films,” Journal of Physical Chemistry B, vol. 104, no. 3, pp. 538–547, 2000.
[64]
R. Zhu, C. Y. Jiang, B. Liu, and S. Ramakrishna, “Highly efficient nanoporous TiO2-polythiophene hybrid solar cells based on interfacial modification using a metal-free organic dye,” Advanced Materials, vol. 21, no. 9, pp. 994–1000, 2009.
[65]
C. Goh, S. R. Scully, and M. D. McGehee, “Effects of molecular interface modification in hybrid organic-inorganic photovoltaic cells,” Journal of Applied Physics, vol. 101, no. 11, Article ID 114503, 2007.
[66]
P. Liska, K. R. Thampi, M. Gr？tzel et al., “Nanocrystalline dye-sensitized solar cell/copper indium gallium selenide thin-film tandem showing greater than 15% conversion efficiency,” Applied Physics Letters, vol. 88, no. 20, Article ID 203103, 2006.
[67]
G. Yu, J. Gao, J. C. Hummelen, F. Wudl, and A. J. Heeger, “Polymer photovoltaic cells: enhanced efficiencies via a network of internal donor-acceptor heterojunctions,” Science, vol. 270, no. 5243, pp. 1789–1791, 1995.
[68]
Y. X. Liu, M. A. Summers, S. R. Scully, and M. D. McGehee, “Resonance energy transfer from organic chromophores to fullerene molecules,” Journal of Applied Physics, vol. 99, no. 9, Article ID 093521, 2006.
[69]
S. Lu and A. Madhukar, “Nonradiative resonant excitation transfer from nanocrystal quantum dots to adjacent quantum channels,” Nano Letters, vol. 7, no. 11, pp. 3443–3451, 2007.
[70]
J. Van de Lagemaat, K. D. Benkstein, and A. J. Frank, “Relation between particle coordination number and porosity in nanoparticle films: implications to dye-sensitized solar cells,” Journal of Physical Chemistry B, vol. 105, no. 50, pp. 12433–12436, 2001.
[71]
J. H. Yum, P. Walter, S. Huber et al., “Efficient far red sensitization of nanocrystalline TiO2 films by an unsymmetrical squaraine dye,” Journal of the American Chemical Society, vol. 129, no. 34, pp. 10320–10321, 2007.
[72]
G. K. Mor, O. K. Varghese, M. Paulose, and C. A. Grimes, “Transparent highly ordered TiO2 nanotube arrays via anodization of titanium thin films,” Advanced Functional Materials, vol. 15, no. 8, pp. 1291–1296, 2005.
[73]
K. Shankar, J. Bandara, M. Paulose et al., “Highly efficient solar cells using TiO2 nanotube arrays sensitized with a donor-antenna dye,” Nano Letters, vol. 8, no. 6, pp. 1654–1659, 2008.
[74]
U. Bach, D. Lupo, P. Comte et al., “Solid-state dye-sensitized mesoporous TiO2 solar cells with high photon-to-electron conversion efficiencies,” Nature, vol. 395, no. 6702, pp. 583–585, 1998.
[75]
A. Inoue, T. Hosokawa, M. Haishi, and N. Ohtani, “4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM)-doping density dependence of luminescence spectra and white emission in polymer light-emitting diodes,” Physica Status Solidi (C), vol. 6, no. 1, pp. 334–337, 2009.
[76]
H. J. Snaith, A. Petrozza, S. Ito, H. Miura, and M. Gra？tzel, “Charge generation and photovoltaic operation of solid-state dye-sensitized solar cells incorporating a high extinction coefficient indolene-based sensitizer,” Advanced Functional Materials, vol. 19, no. 11, pp. 1810–1818, 2009.
[77]
H. J. Snaith, R. Humphry-Baker, P. Chen, I. Cesar, S. M. Zakeeruddin, and M. Gr？tzel, “Charge collection and pore filling in solid-state dye-sensitized solar cells,” Nanotechnology, vol. 19, no. 42, Article ID 424003, 2008.
[78]
H. J. Snaith, A. J. Moule, C. Klein, K. Meerholz, R. H. Friend, and M. Gr？tzel, “Efficiency enhancements in solid-state hybrid solar cells via reduced charge recombination and increased light capture,” Nano Letters, vol. 7, no. 11, pp. 3372–3376, 2007.
[79]
W. M. Campbell, K. W. Jolley, P. Wagner et al., “Highly efficient porphyrin sensitizers for dye-sensitized solar cells,” Journal of Physical Chemistry C, vol. 111, no. 32, pp. 11760–11762, 2007.
[80]
D. M. Huang, H. J. Snaith, M. Gr？tzel, K. Meerholz, and A. J. Mou？, “Optical description of solid-state dye-sensitized solar cells. II. Device optical modeling with implications for improving efficiency,” Journal of Applied Physics, vol. 106, no. 7, Article ID 073112, 2009.
[81]
R. H. Lohwasser, J. Bandara, and M. Thelakkat, “Tailor-made synthesis of poly(3-hexylthiophene) with carboxylic end groups and its application as a polymer sensitizer in solid-state dye-sensitized solar cells,” Journal of Materials Chemistry, vol. 19, no. 24, pp. 4126–4130, 2009.
[82]
H. Lee, H. C. Leventis, S. J. Moon et al., “PbS and CdS quantum dot-sensitized solid-state solar cells: “Old concepts, new results”,” Advanced Functional Materials, vol. 19, no. 17, pp. 2735–2742, 2009.
[83]
I. K. Ding, N. Tétreault, J. Brillet et al., “Pore-filling of spiro-OMeTAD in solid-state dye sensitized solar cells: quantification, mechanism, and consequences for device performance,” Advanced Functional Materials, vol. 19, no. 15, pp. 2431–2436, 2009.
[84]
D. Kuang, P. Walter, F. Nüesch et al., “Co-sensitization of organic dyes for efficient ionic liquid electrolyte-based dye-sensitized solar cells,” Langmuir, vol. 23, no. 22, pp. 10906–10909, 2007.
[85]
J. H. Yum, S. R. Jang, P. Walter et al., “Efficient co-sensitization of nanocrystalline TiO2 films by organic sensitizers,” Chemical Communications, no. 44, pp. 4680–4682, 2007.
[86]
A. Burke, L. Schmidt-Mende, S. Ito, and M. Gr？tzel, “A novel blue dye for near-IR 'dye-sensitised' solar cell applications,” Chemical Communications, no. 3, pp. 234–236, 2007.
[87]
C. Siegers, U. Würfel, M. Zistler et al., “Overcoming kinetic limitations of electron injection in the dye solar cell via coadsorption and FRET,” ChemPhysChem, vol. 9, no. 5, pp. 793–798, 2008.
[88]
S. Honda, T. Nogami, H. Ohkita, H. Benten, and S. Ito, “Improvement of the light-harvesting efficiency in polymer/fullerene bulk heterojunction solar cells by interfacial dye modification,” ACS Applied Materials & Interfaces, vol. 1, pp. 804–810, 2009.
[89]
D. Poplavskyy and J. Nelson, “Nondispersive hole transport in amorphous films of methoxy-spirofluorene-arylamine organic compound,” Journal of Applied Physics, vol. 93, no. 1, pp. 341–346, 2003.
[90]
J. García-Ca？adas, F. Fabregat-Santiago, H. J. Bolink, E. Palomares, G. Garcia-Belmonte, and J. Bisquert, “Determination of electron and hole energy levels in mesoporous nanocrystalline TiO2 solid-state dye solar cell,” Synthetic Metals, vol. 156, no. 14-15, pp. 944–948, 2006.
[91]
U. B. Cappel, E. A. Gibson, A. Hagfeldt, and G. Boschloo, “Dye regeneration by Spiro-MeOTAD in solid state dye-sensitized solar cells studied by photoinduced absorption spectroscopy and spectroelectrochemistry,” Journal of Physical Chemistry C, vol. 113, no. 15, pp. 6275–6281, 2009.
[92]
J. Bourson and B. Valeur, “Ion-responsive fluorescent compounds. 2. Cation-steered intramolecular charge transfer in a crowned merocyanine,” Journal of Physical Chemistry, vol. 93, no. 9, pp. 3871–3876, 1989.
[93]
H. J. Snaith and L. Schmidt-Mende, “Advances in liquid-electrolyte and solid-state dye-sensitized solar cells,” Advanced Materials, vol. 19, no. 20, pp. 3187–3200, 2007.
[94]
T. Park, S. A. Haque, R. J. Potter, A. B. Holmes, and J. R. Durrant, “A supramolecular approach to lithium ion solvation at nanostructured dye sensitised inorganic/organic heterojunctions,” Chemical Communications, vol. 9, no. 23, pp. 2878–2879, 2003.
[95]
C. S. Karthikeyan and M. Thelakkat, “Key aspects of individual layers in solid-state dye-sensitized solar cells and novel concepts to improve their performance,” Inorganica Chimica Acta, vol. 361, no. 3, pp. 635–655, 2008.
[96]
J. Krüger, R. Plass, L. Cevey, M. Piccirelli, M. Gr？tzel, and U. Bach, “High efficiency solid-state photovoltaic device due to inhibition of interface charge recombination,” Applied Physics Letters, vol. 79, no. 13, pp. 2085–2087, 2001.
[97]
H. J. Snaith and M. Gr？tzel, “Enhanced charge mobility in a molecular hole transporter via addition of redox inactive ionic dopant: Implication to dye-sensitized solar cells,” Applied Physics Letters, vol. 89, no. 26, Article ID 262114, 2006.
[98]
E. T. Hoke, B. E. Hardin, and M. D. McGehee, “Modeling the efficiency of F？rster resonant energy transfer from energy relay dyes in dyesensitized solar cells,” Optics Express, vol. 18, no. 4, pp. 3893–3904, 2010.
[99]
M. Gr？tzel, “Conversion of sunlight to electric power by nanocrystalline dye-sensitized solar cells,” Journal of Photochemistry and Photobiology A, vol. 164, no. 1–3, pp. 3–14, 2004.
[100]
G. Rottenkolber, R. Meier, O. Schafer, S. Wachter, K. Dullenkopf, and S. Wittig, Laser Techniques for Fluid Dynamics, R. J. Adrian, D. F. G. Durao, F. Durst, M. V. Heitor, M. Maeda and J. H. Whitelaw, Eds, Springer, Berlin, Germany, 2002.
[101]
J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Springer, Berlin, Germany, 3rd edition, 2006.
[102]
K. Shankar, J. Bandara, M. Paulose et al., “Highly efficient solar cells using TiO2 nanotube arrays sensitized with a donor-antenna dye,” Nano Letters, vol. 8, no. 6, pp. 1654–1659, 2008.
[103]
H. Kuhn, “Classical aspects of energy transfer in molecular systems,” The Journal of Chemical Physics, vol. 53, no. 1, pp. 101–108, 1970.
[104]
B. Wenger, M. Gr？tzel, and J.-E. Moser, “Rationale for kinetic heterogeneity of ultrafast light-induced electron transfer from Ru(II) complex sensitizers to nanocrystalline TiO2,” Journal of the American Chemical Society, vol. 127, no. 35, pp. 12150–12151, 2005.
[105]
M. Ikeda, N. Koide, L. Han, A. Sasahara, and H. Onishi, “Scanning tunneling microscopy study of black dye and deoxycholic acid adsorbed on a rutile TiO2(110),” Langmuir, vol. 24, no. 15, pp. 8056–8060, 2008.
[106]
D. A. Fernández, J. Awruch, and L. E. Dicelio, “Photophysical and aggregation studies of t-butyl-substituted Zn phthalocyanines,” Photochemistry and Photobiology, vol. 63, no. 6, pp. 784–792, 1996.
[107]
M. K. Nazeeruddin, F. De Angelis, S. Fantacci et al., “Combined experimental and DFT-TDDFT computational study of photoelectrochemical cell ruthenium sensitizers,” Journal of the American Chemical Society, vol. 127, no. 48, pp. 16835–16847, 2005.
[108]
M. K. Nazeeruddin, A. Kay, I. Rodicio et al., “Conversion of light to electricity by cis-X2bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) charge-transfer sensitizers (X = Cl-, Br-, I-, CN-, and SCN-) on nanocrystalline TiO2 electrodes,” Journal of the American Chemical Society, vol. 115, no. 14, pp. 6382–6390, 1993.
[109]
A. C. Fisher, L. M. Peter, E. A. Ponomarev, A. B. Walker, and K. G. U. Wijayantha, “Intensity dependence of the back reaction and transport of electrons in dye-sensitized nanocrystalline TiO2 Solar Cells,” Journal of Physical Chemistry B, vol. 104, no. 5, pp. 949–958, 2000.
[110]
M. Law, L. E. Greene, J. C. Johnson, R. Saykally, and P. Yang, “Nanowire dye-sensitized solar cells,” Nature Materials, vol. 4, no. 6, pp. 455–459, 2005.
[111]
M. Adachi, Y. Murata, I. Okada, and S. Yoshikawa, “Formation of titania nanotubes and applications for dye-sensitized solar cells,” Journal of the Electrochemical Society, vol. 150, no. 8, pp. G488–G493, 2003.
[112]
O. K. Varghese, M. Paulose, T. J. LaTempa, and C. A. Grimes, “High-rate solar photocatalytic conversion of CO2 and water vapor to hydrocarbon fuels,” Nano Letters, vol. 9, no. 2, pp. 731–737, 2009.
[113]
C. S. Karthikeyan, H. Wietasch, and M. Thelakkat, “Highly efficient solid-state dye-sensitized TiO2 solar cells using donor-antenna dyes capable of multistep charge-transfer cascades,” Advanced Materials, vol. 19, no. 8, pp. 1091–1095, 2007.
[114]
S. Handa, H. Wietasch, M. Thelakkat, J. R. Durrant, and S. A. Haque, “Reducing charge recombination losses in solid state dye sensitized solar cells: the use of donor-acceptor sensitizer dyes,” Chemical Communications, no. 17, pp. 1725–1727, 2007.
[115]
S. A. Haque, S. Handa, K. Peter, E. Palomares, M. Thelakkat, and J. R. Durrant, “Supermolecular control of charge transfer in dye-sensitized nanocrystalline TiO2 films: towards a quantitative structure-function relationship,” Angewandte Chemie - International Edition, vol. 44, no. 35, pp. 5740–5744, 2005.
[116]
C. S. Karthikeyan, K. Peter, H. Wietasch, and M. Thelakkat, “Highly efficient solid-state dye-sensitized TiO2 solar cells via control of retardation of recombination using novel donor-antenna dyes,” Solar Energy Materials and Solar Cells, vol. 91, no. 5, pp. 432–439, 2007.
[117]
A. Zaban, S. G. Chen, S. Chappel, and B. A. Gregg, “Bilayer nanoporous electrodes for dye sensitized solar cells,” Chemical Communications, no. 22, pp. 2231–2232, 2000.
[118]
S. G. Chen, S. Chappel, Y. Diamant, and A. Zaban, “Preparation of Nb2O5 coated TiO2 nanoporous electrodes and their application in dye-sensitized solar cells,” Chemistry of Materials, vol. 13, no. 12, pp. 4629–4634, 2001.
[119]
U. Diebold, “The surface science of titanium dioxide,” Surface Science Reports, vol. 48, no. 5–8, pp. 53–229, 2003.
[120]
C. Bauer, G. Boschloo, E. Mukhtar, and A. Hagfeldt, “Electron injection and recombination in Ru(dcbpy)2(NCS)2 sensitized nanostructured Zno,” Journal of Physical Chemistry B, vol. 105, no. 24, pp. 5585–5588, 2001.
[121]
T. P. Chou, Q. Zhang, and G. Cao, “Effects of dye loading conditions on the energy conversion efficiency of ZnO and TiO2 dye-sensitized solar cells,” Journal of Physical Chemistry C, vol. 111, no. 50, pp. 18804–18811, 2007.
[122]
N. G. Park, J. Van De Lagemaat, and A. J. Frank, “Comparison of dye-sensitized rutile- and anatase-based TiO2 solar cells,” Journal of Physical Chemistry B, vol. 104, no. 38, pp. 8989–8994, 2000.
