Effect of TiO2 colloids on the fluorescence behavior of two cyanine dyes

The photophysical properties of two typical cyanine dyes [3,3'-diethyl-9-methyl-thiacarbocyanine iodide (dye A) and anhydro-3,3'-disulfopropyl-5,5'-diphenyl-9-ethyloxacarbocyanine hydroxide (dye B)] in the absence and presence of TiO(2) colloids have been investigated by UV-visible spectroscopy, (1)H-NMR spectroscopy, fluorescence spectroscopy, fluorescence lifetime measurements, and ESR measurements. It was found from the absorption spectra and NMR results that there are two isomers in the ground state of these dyes. Steady-state fluorescence spectra show that the fluorescence intensities of dye A and dye B are enhanced and quenched by TiO(2) colloids, respectively. Time-resolved fluorescence lifetime measurements indicate that the lifetimes of dye A and dye B in the presence of TiO(2) colloids are longer and shorter than those obtained in the absence of TiO(2) colloids, respectively. ESR measurements demonstrate that the electron transfer efficiency from (1)dye B* to the conduction band of TiO(2) is much larger than that from (1)dye A* to the conduction band of TiO(2). The different fluorescence behavior of dye A and dye B can be intepreted in terms of whether phi(Tr,nr)(0)-phi(Tr,nr) (the reduction of the quantum yield for radiationless transition in the excited singlet state (1)dye* caused by the TiO(2) colloids) is larger or smaller than phi(ET) (the quantum yield of electron transfer from (1)dye* to the conduction band of TiO(2) colloids).     

Electron transport in coumarin-dye-sensitized nanocrystalline TiO2 electrodes

We investigated electron transport kinetics in terms of electron diffusion coefficient (D) and electron lifetime (tau) in coumarin-dye-sensitized nanocrystalline TiO2 electrodes by intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS). We found that the values of tau for coumarin-dye-sensitized TiO2 electrodes were much shorter than that for an electrode coated with a Ru complex (N719 dye), suggesting that the back-electron-transfer process corresponding to recombination between conduction-band electrons in the TiO2 and I3- ions in the electrolyte occurs more easily in coumarin-dye-sensitized solar cells. In addition, the values of tau depended on the kind of coumarin dye, each of which has a different number of thiophene moieties, suggesting that the molecular structure of the adsorbed dyes also affects the kinetics of electron transport in the TiO2 electrodes.     

Change of adsorption modes of dyes on fluorinated TiO2 and its effect on photocatalytic degradation of dyes under visible irradiation

Surface-fluorinated TiO2 (F-TiO2) particles were prepared via the HF etching method. The surface characteristics of fluorinated TiO2, the adsorption modes of dyes, and the reaction pathways for the photocatalytic degradation of dye pollutants under visible light irradiation were investigated. It was found that, in the treatment of TiO2 by HF etching, F(-) not only displaces surface HO(-) but also substitutes some surface lattice oxygen. Using zwitterionic Rhodamine B (RhB) dye as a model, the change of the adsorption mode of RhB on F-TiO2 relative to that on pure TiO2 was validated by adsorption isotherms, X-ray photoelectron spectroscopy (XPS), and IR techniques for the first time. RhB preferentially anchors on pure TiO2 through the carboxylic (-COOH) group, while its adsorption group is switched to the cationic moiety (-NEt 2 group) on F-TiO2. Both the photocatalytic degradation kinetics and mechanisms were drastically changed after surface fluorination. Dyes with positively charged nitrogen-alkyl groups such as methylene blue (MB), malachite green (MG), Rhodamine 6G (Rh6G), and RhB all underwent a rapid N-dealkylation process on F-TiO2, while on pure TiO2 direct cleavage of dye chromophore ring structures predominated. The relationship between surface fluorination and the degradation rate/pathway of dyes under visible irradiation was also discussed in terms of the effect of fluorination on the surface adsorption of dyes and on the energy band structure of TiO2.     

Mechanism of TiO2-assisted photocatalytic degradation of dyes under visible irradiation: photoelectrocatalytic study by TiO2-film electrodes

Photoelectrocatalytic degradation of various dyes under visible light irradiation with a TiO(2) nanoparticles electrode has been investigated to reveal the mechanism for TiO(2)-assisted photocatalytic degradation of dyes. The degradation of both cationic and anionic dyes at different biases, including the change in the degradation rate of the dyes and the photocurrent change with the bias potential, the degraded intermediates, the voltage-induced adsorption of dyes, the accumulation of electrons in the TiO(2) electrode, the effect of various additives such as benzoquinone (BQ) and N,N-dimethyl aniline (DMA), and the formation of active oxygen species such as O(2)(*-) and H(2)O(2) were examined by UV-visible spectroscopy, HPLC, TOC, and spin-trap ESR spectrometry. It was found that the dyes could controllably interact with the TiO(2) surface by external bias changes and charging of dyes. The cationic dyes such as RhB and MG underwent efficient mineralization at negative bias, but the N-dealkylation process predominated at positive bias under visible light irradiation. The discolorations of the anionic dyes SRB and AR could not be accelerated significantly at either negative or positive bias. At a negative bias of -0.6 V vs SCE, O(2)(*-) and dye(*+) were formed simultaneously at the electrode/electrolyte interface during degradation of cationic RhB. In the case of anionic dyes, however, it is impossible for the O(2)(*-) and dye cationic radical to coexist at the electrode/electrolyte surface. Experimental results imply both the superoxide anionic radical and the dye cationic radical are essential to the mineralization of the dyes under visible light-induced photocatalytic conditions.     

Oligothiophene-containing coumarin dyes for efficient dye-sensitized solar cells

We have developed oligothiophene-containing coumarin dyes fully functionalized for dye-sensitized nanocrystalline TiO(2) solar cells (DSSCs). DSSCs based on the dyes gave good performance in terms of incident photon-to-current conversion efficiency (IPCE) in the range of 400-800 nm. A solar energy-to-electricity conversion efficiency (eta) of 7.4% was obtained with a DSSC based on 2-cyano-3-[5'-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)-[2,2']bithiophenyl-5-yl]acrylic acid (NKX-2677) under simulated AM 1.5G irradiation (100 mW cm(-2)) with a mask: short-circuit current density (J(sc)) = 13.5 mA cm(-2); open-circuit voltage (V(oc)) = 0.71 V; fill factor (FF) = 0.77. Transient absorption spectroscopy measurements indicated that electron injection from NKX-2677 to the conduction band of TiO(2) is very rapid (<100 fs), which is much faster than the emission lifetime of the dye (1.0 ns), giving a highly efficient electron injection yield of near unity.     

二氢吲哚类染料用于染料敏化太阳能电池光敏剂的比较

采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对四种二氢吲哚染料进行研究, 从中筛选出相对优秀的染料敏化太阳能电池光敏剂. 对前线分子轨道的计算表明, 二氢吲哚染料的前线分子轨道结构非常有利于染料激发态向TiO2电极的电子注入. 对真空中的紫外和可见光吸收光谱的计算表明, 二氢吲哚染料的吸收光谱与太阳辐射光谱匹配较好. 对染料分子的能级计算表明, 二氢吲哚染料的能级结构比较适合于I-/I-3作电解液的TiO2纳米晶太阳能电池的光敏剂. 二氢吲哚染料最低未占据分子轨道(LUMO) 能级均比TiO2晶体导带边能级高, 能够保证激发态染料分子高效地向TiO2电极转移电子. 二氢吲哚染料最高占据分子轨道(HOMO)的能级比I-/I-3能级低, 保证了失去电子的染料分子能够顺利地从电解液中得到电子. 与实验数据比较, 得出在提高染料敏化太阳能电池转换效率方面, 对染料的关键要求是LUMO能级的位置. 染料分子的稳定性是染料敏化太阳能电池使用寿命的关键因素. 通过对化学键键长的比较表明, 二氢吲哚染料的分子稳定性基本相同. 对计算结果的分析表明, 二氢吲哚染料1(ID1)的LUMO能级最高, 分子稳定性最好, 在酒精溶液中的吸收光谱与太阳辐射光谱匹配很好, 在同类染料中是较好的染料敏化太阳能电池光敏剂.     

Characterization of solid-state dye-sensitized solar cells utilizing high absorption coefficient metal-free organic dyes

Solid-state dye-sensitized solar cells were fabricated using the organic hole-transporting medium (HTM) 2,2'7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD), and three organic indoline-based sensitizer dyes with high molar extinction coefficients. The cells were characterized by several techniques, including spectral response measurements, photovoltage decay transients, intensity modulated photovoltage spectroscopy (IMVS), and charge extraction. The differences in apparent electron lifetime observed for cells fabricated using the three dyes are attributed in part to changes in the surface dipole potential at the TiO2/spiro-MeOTAD interface, which shift the TiO2 conduction band energy relative to the Fermi level of the HTM. These energy shifts influence both the open circuit voltage (as a result of changes in free electron density) and the short circuit current (as a consequence of changes in the overlap between the dye LUMO level and the conduction band). A self-consistent approach was used to derive the positions of the conduction band relative to the spiro-MeOTAD redox Fermi level for cells fabricated using the three dyes. The analysis also provided estimates of the free electron lifetime in spiro-MeOTAD cells. In order to evaluate the possible contribution of the adsorbed dyes to the observed changes in surface dipole potential, their dipole moments were estimated using ab initio density functional theory (DFT) calculations. Comparison of the calculated dipole contributions with the experimentally measured shifts in conduction band energy revealed that other factors such as proton adsorption may be predominant in determining the surface dipole potential.     

Porphyrins for dye-sensitised solar cells: new insights into efficiency-determining electron transfer steps

Porphyrin molecules offer immense potential as the light harvesting component of dye-sensitised nanocrystalline TiO(2) solar cells. Synthetic porphyrin dyes were amongst the first dyes trialled for sensitisation of inorganic semiconducting oxides. Today, they exhibit the best performance reported for dye-sensitised solar cells. Accompanying the significant performance improvement over the last two decades is a much improved understanding of efficiency-determining fundamental electron transfer steps, from charge photogeneration to recombination. In this feature article we highlight our recent discoveries of the influence of porphyrin molecule structure on efficiency determining electron transfer kinetics and device performance by systematically changing the molecular structure and observing electron injection and recombination kinetics using time-resolved optical and electrical probes. Despite our observation of ultrafast charge injection for all porphyrin dyes studied by transient absorption spectroscopy, the injection yield estimated using an internal standard remains below 100% and depends strongly on the molecular structure. The observed discrepancy between kinetic competition and the injection yield is attributed to non-injecting dyes, probably arising due to inhomogeneity. A very interesting sub-ns (0.5 ns to 100 ns) charge recombination channel between photo-injected electrons and porphyrin cations is observed, which is found to be more prominent in free-base porphyrin dyes with a conjugated linker. Charge recombination between the acceptor species in the redox containing electrolyte and injected electrons is shown to be an important limitation of most porphyrin-sensitised solar cells, accelerated by the presence of porphyrin molecules at the TiO(2)-electrolyte interface. This recombination reaction is strongly dependent on the porphyrin molecular structure. Bulky substituents, using a porphyrin dimer instead of a porphyrin monomer, a light soaking treatment of freshly prepared films and co-sensitization of TiO(2) with multiple dyes are shown to be successful strategies to improve electron lifetime. Finally, new developments unique to porphyrin dye-sensitised solar cells, including performance enhancements from a light exposure treatment of a zinc porphyrin dye, a significant performance improvement observed after co-sensitisation of TiO(2) with free-base and zinc porphyrin dyes and the use of porphyrin dimers with increased light harvesting in thin-film TiO(2) solar cells are described.     

Electrophoretic deposition of TiO2 nanoparticles using organic dyes

Electrophoretic deposition method has been developed for the deposition of TiO(2) nanoparticles modified with organic dyes. Alizarin red, alizarin yellow and pyrocatechol violet dyes were used for the dispersion and charging of TiO(2) in ethanol and anodic electrophoretic deposition of TiO(2) films. The deposition yield was varied by the variation of dye concentration in suspensions and deposition time. Aurintricarboxylic acid dye was used for the deposition of TiO(2) from aqueous suspensions. It was found that thin films of pure aurintricarboxylic acid and composite aurintricarboxylic acid TiO(2) films can be obtained. The deposition yield was studied by quartz crystal microbalance. Dye film thickness was varied in the range of 0.1-2 μm by variation in the deposition time at a constant voltage. The composition of the films and the amount of the deposited material can be varied by the variation of TiO(2) and dye concentration in suspensions and deposition time. The films were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and electron microscopy. The deposition mechanisms were discussed. The electrophoretic deposition method offers advantages for the fabrication of dye-sensitized TiO(2) films.     

方菁染料敏化二氧化钛超微粒的光化学行为

通过吸收光谱、荧光猝灭、单光子计数等手段研究了2-(4-乙胺-2-羟基苯基)-4-(4-乙胺-苯基)-方菁染料(SQ)在TiO2超微粒体系中的光化学行为。结果表明, SQ强烈吸附在TiO2胶粒表面, 表观吸附常数为2.275×10^3mol^-^1 . dm^3。SQ的荧光能被TiO2有效地猝灭,猝灭的效率达97%。根据物质的氧化还原电位、光谱特性及荧光寿命的变化提出光诱导电子界面转移的荧光猝灭机理, 电子转移的速率常数为1.97×10^8s^-^1。     

On the alkali instability of phenoxazine dyes as adsorbates of chemically modified electrodes

The alkali instability of phenoxazine dyes was investigated with respect to their application as catalysts for anodic NADH oxidation. Spectrophotometric measurements were used in aqueous solutions at different pH values together with cyclovoltammograms of the dyes adsorbed on a graphite electrode. It is shown that the reason for desactivation in the case of Meldola Blue is a cation-pseudobase equilibrium followed by a ring-opening tautomerism. The open-ring isomer, an unstable o,p′-quinoneanile dye, could be isolated as a dark blue precipitate. Also a by-product (“dimethyl”-Nile Red V) was identified. In the case of phenoxazine dyes substituted with an amino or acylamino group in p-position to the heterocyclic nitrogen, the reason for desactivation of the electrodes is the known reversible formation of a quinone diimine as an anhydrobase.     

Scanning tunneling microscopy study of black dye and deoxycholic acid adsorbed on a rutile TiO2(110)

Trithiocyanato(4,4',4'-tricarboxy-2,2':6',2'-terpyridine)ruthenium(II), "black dye", was adsorbed on a rutile TiO(2)(110) surface and imaged by an ultrahigh vacuum scanning tunneling microscope. The TiO(2)(110)-(1 x 1) surface was prepared in a vacuum, covered with pivalate monolayer, and immersed in acetonitrile containing black dye. Black dyes exchanging preadsorbed pivalates were observed on the surface as protrusions with lateral dimensions from 2 to 10 nm. Protrusions with a minimum lateral dimension of 2 nm were assigned to single, isolated black dyes, and larger protrusions were attributed to aggregated dyes. When deoxycholic acid was added to the dye solution, the number ratio of the single dyes to the aggregated dyes increased, while adsorbed deoxycholic acid was not observed.     

Charge transfer dynamics of model charge transfer centers of a multicenter water splitting dye complex on rutile TiO2(110)

Charge transfer dynamics between an adsorbed molecule and a rutile TiO(2)(110) surface have been investigated in three organometallic dyes related to multicenter water splitting dye complexes: Ru 535 (cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)), Ru 455 (cis-bis(2,2'-bipyridyl)-(2,2'-bipyridyl-4,4'-dicarboxylic acid)-ruthenium(II)), and Ru 470 (tris(2,2'-bipyridyl-4,4'-dicarboxylic acid)-ruthenium(II)). The adsorption of the dye molecules on the rutile TiO(2)(110) surface has been studied using core-level and valence photoemission. Dye molecules were deposited in situ using ultrahigh vacuum electrospray deposition. Core-level photoemission spectra reveal that each complex bonds to the surface via deprotonation of two carboxylic groups. All three dye complexes show evidence of ultrafast charge transfer to the TiO(2) substrate using the core-hole clock implementation of resonant photoemission spectroscopy.     

Multichromophore light harvesting in hybrid solar cells

A new technologically relevant method for multichromophore sensitizing of hybrid blend solar cells is presented. Two dyes having complementary absorption in the UV-visible regions are individually adsorbed on nanocrystalline TiO(2) powder. These dyed TiO(2) nanoparticles are blended with an organic hole-conductor (HC) Spiro-OMeTAD in desired compositions and applied on a conducting substrate by doctor-blading at room temperature to fabricate multichromophore-sensitized hybrid blend solar cells. The external quantum efficiency (EQE) of the single hybrid layer system fabricated with two dyes, that absorb mainly UV (TPD dye) and visible regions (Ru-TPA-NCS dye), exhibited a clear panchromatic response with the sum of the EQE characteristics of each single dye cell. The first results of a multichromophore-sensitized solid-state solar cell showed J(sc) of 2.1 mA cm(-2), V(oc) of 645 mV, FF of 47% and efficiency of 0.65% at AM 1.5 G, 100 mW cm(-2) illumination intensity. The J(sc) of the multichromophore cell is the sum of the individually dyed solar cells. The process described here is technically very innovative and very simple in procedure. It has potentials to be adopted for panchromatic sensitization using more than two dyes in a single hybrid layer or layer-wise fabrication of a tandem structure at room temperature.     

Tuning the HOMO energy levels of organic dyes for dye-sensitized solar cells based on Br-/Br3- electrolytes

A series of novel metal-free organic dyes TC301-TC310 with relatively high HOMO levels were synthesized and applied in dye-sensitized solar cells (DSCs) based on electrolytes that contain Br(-)/Br(3)(-) and I(-)/I(3)(-). The effects of additive Li(+) ions and the HOMO levels of the dyes have an important influence on properties of the dyes and performance of DSCs. The addition of Li(+) ions in electrolytes can broaden the absorption spectra of the dyes on TiO(2) films and shift both the LUMO levels of the dyes and the conduction band of TiO(2), thus leading to the increase of J(sc) and the decrease of V(oc). Upon using Br(-)/Br(3)(-) instead of I(-)/I(3)(-), a large increase of V(oc) is attributed to the enlarged energy difference between the redox potentials of electrolyte and the Fermi level of TiO(2), as well as the suppressed electron recombination. Incident photon to current efficiency (IPCE) action spectra, electrochemical impedance spectra, and nanosecond laser transient absorption reveal that both the electron collection yields and the dye regeneration yields (Φ(r)) depend on the potential difference (the driving forces) between the oxidized dyes and the Br(-)/Br(3)(-) redox couple. For the dyes for which the HOMO levels are more positive than the redox potential of Br(-)/Br(3)(-) sufficient driving forces lead to the longer effective electron-diffusion lengths and almost the same efficient dye regenerations, whereas for the dyes for which the HOMO levels are similar to the redox potential of Br(-)/Br(3)(-), insufficient driving forces lead to shorter effective electron-diffusion lengths and inefficient dye regenerations.     

Kinetics of heterogeneous photocatalytic degradation of reactive dyes in an immobilized TiO2 photocatalytic reactor

The photocatalytic degradation of two reactive dyes has been investigated by UV/TiO2/H2O2 using an immobilized TiO2 photocatalytic reactor. Reactive Blue 8 (RB 8) and Reactive Blue 220 (RB 220) textile dyes were used as model compounds. Photocatalytic degradation processes were performed using a 5-L solution containing dyes. The initial concentrations of dyes were 50 mg/L. The radiation source was two 15 W UV-C lamps. A batch mode immersion photocatalytic reactor was utilized. UV-vis and ion chromatography (IC) analyses were employed to obtain the details of the photodegradation of the selected dyes. Colored synthetic waters were completely decolorized in relatively short time after UV irradiation in the presence of various concentrations of hydrogen peroxide. Formate, acetate, oxalate, and glyoxylate anions were detected as dominant aliphatic intermediates where they were further oxidized slowly to CO2. The UV/TiO2/H2O2 process was able to oxidize the dyes with partial mineralization of carbon, nitrogen, and sulfur heteroatoms into CO2, NO3-, and SO4(2-), respectively. Kinetics analysis indicates that the photocatalytic decolorization rates of the dye can be approximated by a pseudo-first-order model. The UV/TiO2/H2O2 process proved to be capable of decolorization and mineralization of the reactive dyes (RB 8 and RB 220).     

Electrospun nanofibers of TiO2/CdS heteroarchitectures with enhanced photocatalytic activity by visible light

Herein, we have demonstrated that the electrospun nanofibers of TiO(2)/CdS heteroarchitectures could be fabricated through combining electrospinning technique with hydrothermal process. The configuration, crystal structure, and element composition of the as-prepared TiO(2)/CdS heteroarchitectures were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), resonant Raman spectrometer, X-ray photoelectron spectroscopy (XPS). The results indicated that the high-density hexagonal wurtzite CdS crystalline particles of ca. 6-40 nm in diameter were uniformly and closely grown on anatase TiO(2) nanofibers. Especially, the light-absorption properties as well as photocatalytic characteristics of pure TiO(2) nanofibers and TiO(2)/CdS heteroarchitectures with different amount loading of CdS were also investigated. The absorption of TiO(2)/CdS heteroarchitectures was extended to the visible due to effective immobilization of sensitizing agent CdS on TiO(2). In contrast with the pure TiO(2) nanofibers, the TiO(2)/CdS heteroarchitectures showed excellent photocatalytic activity by using rhodamine B dye as a model organic substrate under visible-light irradiation. It was worth noting that the cooperative photocatalytic mechanism of the TiO(2)/CdS heteroarchitectures was also discussed.     

Energy alignment and surface dipoles of rylene dyes adsorbed to TiO2 nanoparticles

The energy loss in dye-sensitized solar cells calculated from the energy difference between the lowest electronic transition of the dye and the obtained open-circuit voltage is often 1 eV or even more. To minimize this loss, it is important to accurately determine the energy alignment at the TiO(2)/dye/redox-mediator interface. In this study, we compared the results from electrochemistry and photoelectron spectroscopy for determining the energy alignment of three rylene dyes, two of which absorb relatively far in the red. The trends observed with the methods were different, as in the former, the energy alignment is measured relative to an external reference and includes contributions from solvent reorganization energies, while in the latter, it is measured relative to the energetics of the TiO(2) and is lacking such contributions. The influence of the dyes' dipole moments on the energetics of the TiO(2) was also measured and explained some of the differences in trends. Finally, we compared the injection efficiencies of the two red-absorbing dyes and found that the differences in injection efficiencies can be better explained using the energy alignment determined from photoelectron spectroscopy. This shows that the method for measuring the energetics of a DSC should be chosen according to what process one intends to study.     

Kinetics of electron recombination of dye-sensitized solar cells based on TiO2 nanorod arrays sensitized with different dyes

The performance and electron recombination kinetics of dye-sensitized solar cells based on TiO(2) films consisting of one-dimensional nanorod arrays (NR-DSSCs) which are sensitized with dyes N719, C218 and D205, respectively, have been studied. It has been found that the best efficiency is obtained with the dye C218 based NR-DSSCs, benefiting from a 40% higher short-circuit photocurrent density. However, the open circuit photovoltage of the N719 based cell is 40 mV higher than that of the organic dye C218 and D205 based devices. Investigation of the electron recombination kinetics of the NR-DSSCs has revealed that the effective electron lifetime, τ(n), of the different dye based NR-DSSCs shows the sequence of C218 > D205 > N719. The higher V(oc) with the N719 based NR-DSSC is originated from the more negative energy level of the conduction band of the TiO(2) film. In addition, in comparison to the DSSCs with the conventional nanocrystalline particles based TiO(2) films, the NR-DSSCs have shown over two orders of magnitude higher τ(n) when employing N719 as the sensitizer. Nevertheless, the τ(n) of the DSSCs with the C218 based nanorod arrays is only ten-fold higher than that of the nanoparticles based devices. The remarkable characteristic of the dye C218 in suppressing the electron recombination of DSSCs is discussed.     

Artificial light-harvesting arrays: electronic energy migration and trapping on a sphere and between spheres

A sophisticated model of the natural light-harvesting antenna has been devised by decorating a C(60) hexa-adduct with ten yellow and two blue boron dipyrromethene (Bodipy) dyes in such a way that the dyes retain their individuality and assist solubility of the fullerene. Unusually, the fullerene core is a poor electron acceptor and does not enter into light-induced electron-transfer reactions with the appended dyes, but ineffective electronic energy transfer from the excited-state dye to the C(60) residue competes with fluorescence from the yellow dye. Intraparticle electronic energy transfer from yellow to blue dyes can be followed by steady-state and time-resolved fluorescence spectroscopy and by excitation spectra for isolated C(60) nanoparticles dissolved in dioxane at 293 K and at 77 K. The decorated particles can be loaded into polymer films by spin coating from solution. In the dried film, efficient energy transfer occurs such that photons absorbed by the yellow dye are emitted by the blue dye. Films can also be prepared to contain C(60) nanoparticles loaded with the yellow Bodipy dye but lacking the blue dye and, under these circumstances, electronic energy migration occurs between yellow dyes appended to the same nanoparticle and, at higher loading, to dye molecules on nearby particles. Doping these latter polymer films with the mixed-dye nanoparticle coalesces these multifarious processes in a single system. Thus, long-range energy migration occurs among yellow dyes attached to different particles before trapping at a blue dye. In this respect, the film resembles the natural photosynthetic light-harvesting complexes, albeit at much reduced efficacy. The decorated nanoparticles sensitize amorphous silicon photocells.