Reference Dye Research Articles

The Effect of Donor Group Rigidification on the Electronic and Optical Properties of Arylamine-Based Metal-Free Dyes for Dye-Sensitized Solar Cells: A Computational Study.

One of the most significant aspects in the development of dye-sensitized solar cells is the exploration and design of high-efficiency and low-cost dyes. This paper reports the theoretical design of various triphenylamine analogues, wherein the central nitrogen moiety establishes an sp(2)-hybridization, which endows a significant participation in the charge-transfer properties. Density functional theory (DFT) and time-dependent DFT methodologies were utilized to investigate the geometry, electronic structure, photochemical properties, and electrochemical properties of these dyes. Different exchange-correlation functionals were initially evaluated to establish a proper methodology for calculating the excited-state energy of the reference dye, known as DIA3. Consequently, TD-LC-ωPBE with a damping parameter of 0.175 Bohr(-1) best correlates with the experimental value. Four new dyes, namely, Dhk1, Dhk2, Dhk3, and Dhk4, were designed by modifying the rigidity of the donor moiety. According to the results, altering the type and position of binding in the donor group leads to distinct planarity of the dyes, which significantly affects their properties. The designed Dhk4 dye showed more red-shifted and broadened absorption spectra owing to the enhanced coplanarity between its donor and π-bridge moiety, which brings an advantage for its potential use as sensitizer for photovoltaic applications.

A Novel Ratiometric Oxygen Sensor Based On a Sextuple Hydrogen‐Bonding Self‐Assembly Molecular Heterodimer

AbstractA novel sextuple hydrogen‐bonding (HB) self‐assembly molecular heterodimer bearing an iridium complex as the indicator dye and two carbazoles as the reference dye, namely 6HB‐Irbt‐Cz, was synthesized, and its molecular structure was confirmed by 1H NMR, 13CNMR, TOF‐MS and 2D NMR. Because of the inefficient energy transfer process between the carbazole and iridium complex units, 6HB‐Irbt‐Cz exhibits distinct ?uorescence/phosphorescence dual emission in neat film state. More importantly, the neat film sample of 6HB‐Irbt‐Cz could display linear ratiometric optical response toward oxygen in the full oxygen concentration range from 0 to 100 vol%, together with good stability, reversibility and rapid response‐recovery times. Note that this represents the first discovery of neat‐film‐based oxygen sensor capable of showing strictly linear ratiometric Stern‐Volmer behavior in the oxygen concentration of 0–100 vol%.

Broad-absorbing tetrabenzocorrolazine green photosensitizer for the enhanced conversion efficiency in dye-sensitized solar cells

Novel tetrabenzocorrolazine green photosensitizer was designed and synthesized to enhance the solar energy-to-electricity conversion efficiency of dye-sensitized solar cells. This near-infrared absorbing dye exhibited superior short-circuit photocurrent density induced from the additional absorption compared to the phthalocyanine dye commonly applied as a photosensitizer covering the near-infrared region in dye-sensitized solar cells. The introduction of bulky peripheral groups and axial substituents to the novel dye led to the increase of open-circuit photovoltage. As a result, the novel tetrabenzocorrolazine dye achieved a solar energy-to-electricity conversion efficiency of 3.78% under AM 1.5G conditions which was much higher than that of the phthalocyanine reference dye.

Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods

We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390–800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min−1, which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

A Hydrogen‐Bonded‐Supramolecular‐Polymer‐Based Nanoprobe for Ratiometric Oxygen Sensing in Living Cells

The first example of a ratiometric optical oxygen nanoprobe based on a hydrogen‐bonded supramolecular polymer has been reported. The supramolecular polymer based nanoprobe (SPNP) is prepared from the co‐assembly of a bis‐ureidopyrimidinone (bis‐UPy)‐containing phosphorescent indicator (Por(Pd)‐bisUPy), fluorescent reference dye (BF2‐bisUPy), and skeleton unit (DPA‐bisUPy) through quadruple hydrogen bonds by a mini‐emulsion method. The water‐dispersible SPNP is highly sensitive to oxygen (Q = 95%), with full reversibility, excellent storage stability and photostability, and good cell‐penetrating ability, and exhibits low cytotoxicity toward living cells. The preparation of the SPNP is straightforward and its function is easily tuned by changing the monomeric structure. This work is expected to lead to the design of other SPNPs for other important analytes in biological systems.

Ratiometric Nanothermometer Based on Rhodamine Dye-Incorporated F127-Melamine-Formaldehyde Polymer Nanoparticle: Preparation, Characterization, Wide-Range Temperature Sensing, and Precise Intracellular Thermometry.

A series of fluorescent nanothermometers (FTs) was prepared with Rhodamine dye-incorporated Pluronic F-127-melamine-formaldehyde composite polymer nanoparticles (R-F127-MF NPs). The highly soluble Rhodamine dye molecules were bound with Pluronic F127 micelles and subsequently incorporated in the cross-linked MF resin NPs during high-temperature cross-link treatment. The morphology and chemical structure of R-F127-MF NPs were characterized with dynamic light scattering, electron microscopy, and Fourier-transform infrared (FTIR) spectra. Fluorescence properties and thermoresponsivities were analyzed using fluorescence spectra. R-F127-MF NPs are found to be monodispersed, presenting a size range of 88-105 nm, and have bright fluorescence and high stability in severe treatments such as autoclave sterilization and lyophilization. By simultaneously incorporating Rhodamine B and Rhodamine 110 (as reference) dyes at a doping ratio of 1:400 in the NPs, ratiometric FTs with a high sensibility of 7.6%·°C(-1) and a wide temperature sensing range from -20 to 110 °C were obtained. The FTs exhibit good stability in solutions with varied pH, ionic strengths, and viscosities and have similar working curves in both intracellular and extracellular environments. Cellular temperature variations in Hela cells during microwave exposure were successfully monitored using the FTs, indicating their considerable potential applications in the biomedical field.

A multi-layer microchip for high-throughput single-cell gene expression profiling

Microfluidics or Bio-MEMS technology offers significant advantages for performing high-throughput screens and sensitive assays. The ability to correlate single-cell genetic information with cellular phenotypes is of great importance to biology and medicine because it holds the potential to gain insight into disease pathways that is unavailable from ensemble measurements. Previously, we reported two kinds of prototypes for integrated on-chip gene expression profiling at the single-cell level, and the throughput was designed to be 6. In this work, we present a five-layer microfluidic system for parallelized, rapid, quantitative analysis of RNA templates with low abundance at the single-cell level. The microchip contains two multiplexors and one partitioning valve group, and it leverages a matrix (6 × 8) of quantitative reverse transcription polymerase chain reaction (RT–qPCR) units formed by a set of parallel microchannels concurrently controlled by elastomeric pneumatic valves, thereby enabling parallelized handling and processing of biomolecules in a simplified operation procedure. A comprehensive metallic nanofilm with passivation layer is used to run polymerase chain reaction (PCR) temperature cycles. To demonstrate the utility of the approach, artificial synthesized RNA templates (XenoRNA) and mRNA templates from single cells are employed to perform the 48-readout RT–qPCRs. The PCR products are imaged on a fluorescence microscope using a hydrolysis probe/primer set (TaqMan). Fluorescent intensities of passive reference dye and a fluorescein amidite reporter dye are acquired and measured at the end of PCR cycles.

Co-sensitization of Dithiafulvenyl-Phenothiazine Based Organic Dyes with N719 for Efficient Dye-Sensitized Solar Cells

The introduction of additional electron donor and elongation of π-conjugated bridge represents a feasible strategy to enhance light harvesting in both breadth and intensity of donor-(π conjugated spacer)-acceptor (D-π-A) dyes suitable for dye-sensitized solar cells (DSSCs). Here, two novel metal-free organic dyes, in which dithiafulvenyl unit was introduced into phenothiazine donor as an additional electron donor, cyanoacrylic acid as the electron acceptor, and without (PTZ-2) or with (PTZ-3) a benzene as the π-linker between phenothiazine donor and cyanoacrylic acid electron-withdrawing group, were synthesized by modifying the simple D-π-A dye (PTZ-1) and successfully utilized in DSSCs. Their photophysical, electrochemical, photovoltaic properties and theoretical calculations were further investigated. Relative to the reference dye PTZ-1, the power conversion efficiencies (PCEs) increased significantly from 4.04% to 5.81% (PTZ-2) and 5.22% (PTZ-3), which came mainly from the enhancement of short-circuit current (Jsc) due to the broader molecular absorption spectra and higher molar extinction coefficients. What's more, it is worth noting that the dyes of PTZ-2 and PTZ-3 have strong absorption, which can compensate for that of N719 in the low wavelength region, especially in the region of ∼300–500nm. Therefore, a co-sensitization approach has been used for achieving enhanced performances in DSSCs wherein N719 was co-sensitized with PTZ-2 and PTZ-3, respectively. Consequently, the co-sensitized DSSC (PTZ–2+N719) gave the highest efficiency of 8.12%, exhibiting an improvement of 16.50% compared to the device sensitized with N719 alone (PCE=6.97%) under the same conditions.

Strongly Coupled Cyclometalated Ruthenium Triarylamine Chromophores as Sensitizers for DSSCs.

A series of anchor-functionalized cyclometalated bis(tridentate) ruthenium(II) triarylamine hybrids [Ru(dbp-X)(tctpy)](2-) [2 a](2-) -[2 c](2-) (H3 tctpy=2,2';6',2''-terpyridine-4,4',4''-tricarboxylic acid; dpbH=1,3-dipyridylbenzene; X=N(4-C6 H4 OMe)2 ([2 a](2-) ), NPh2 ([2 b](2-) ), N-carbazolyl [2 c](2-) ) was synthesized and characterized. All complexes show broad absorption bands in the range 300-700 nm with a maximum at about 545 nm. Methyl esters [Ru(Me3 tctpy)(dpb-X)](+) [1 a](+) -[1 c](+) are oxidized to the strongly coupled mixed-valent species [1 a](2+) -[1 c](2+) and the Ru(III) (aminium) complexes [1 a](3+) -[1 c](3+) at comparably low oxidation potentials. Theoretical calculations suggest an increasing spin delocalization between the metal center and the triarylamine unit in the order [1 a](2+) <[1 b](2+) <[1 c](2+) . Solar cells were prepared with the saponified complexes [2 a](2-) -[2 c](2-) and the reference dye N719 as sensitizers using the I3 (-) /I(-) couple and [Co(bpy)3 ](3+/2+) and [Co(ddpd)2 ](3+/2+) couples as [B(C6 F5 )4 ](-) salts as electrolytes (bpy=2,2'-bipyridine; ddpd=N,N'-dimethyl-N,N'-dipyridin-2-yl-pyridine-2,6-diamine). Cells with [2 c](2-) and I3 (-) /I(-) electrolyte perform similarly to cells with N719. In the presence of cobalt electrolytes, all efficiencies are reduced, yet under these conditions [2 c](2-) outperforms N719.

Does the position of the electron-donating nitrogen atom in the ring system influence the efficiency of a dye-sensitized solar cell? A computational study.

We have reported a number of new metal-free organic dyes (2-6) that have cyclic asymmetric benzotripyrrole derivatives as donor groups with peripheral nitrogen atoms in the ring, fluorine and thiophene groups as π-spacers, and a cyanoacrylic acid acceptor group. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed to examine the influence of the position of the donor nitrogen atom and π-conjugation on solar cell performance. The calculated electron-injection driving force (ΔG inject), electron-regeneration driving force (ΔG regen), light-harvesting efficiency (LHE), dipole moment (μ normal), and number of electrons transferred (∆q) indicate that dyes 3, 4, and 6 have significantly higher efficiencies than reference dye 1, which exhibits high efficiency. We also extended our comparison to some other reported dyes, 7-9, which have a donor nitrogen atom in the middle of the ring system. The computed results suggest that dye 6 possesses a higher incident photon to current conversion efficiency (IPCE) than reported dyes 7-9. Thus, the use of donor groups with peripheral nitrogen atoms appears to lead to more efficient dyes than those in which the nitrogen atom is present in the middle of the donor ring system. Graphical Abstract The locations of the nitrogen atoms in the donor groups in the designed dye molecules have an important influence on DSSC efficiency.

Different Effect of the Additional Electron-Withdrawing Cyano Group in Different Conjugation Bridge: The Adjusted Molecular Energy Levels and Largely Improved Photovoltaic Performance.

Four organic sensitizers (LI-68-LI-71) bearing various conjugated bridges were designed and synthesized, in which the only difference between LI-68 and LI-69 (or LI-70 and LI-71) was the absence/presence of the CN group as the auxiliary electron acceptor. Interestingly, compared to the reference dye of LI-68, LI-69 bearing the additional CN group exhibited the bad performance with the decreased Jsc and Voc values. However, once one thiophene moiety near the anchor group was replaced by pyrrole with the electron-rich property, the resultant LI-71 exhibited a photoelectric conversion efficiency increase by about 3 folds from 2.75% (LI-69) to 7.95% (LI-71), displaying the synergistic effect of the two moieties (CN and pyrrole). Computational analysis disclosed that pyrrole as the auxiliary electron donor (D') in the conjugated bridge can compensate for the lower negative charge in the electron acceptor, which was caused by the CN group as the electron trap, leading to the more efficient electron injection and better photovoltaic performance.

Phenothiazine organic dyes with the cone-shaped structural: Broad photoresponse and limitations on short-circuit photocurrent density in dye-sensitized solar cells

Three novel phenothiazine organic dyes (WR11-13) with the cone-shaped structural have been developed for dye-sensitized solar cells applications. The effect of electron donor alternation on the optical, electrochemical and the photovoltaic properties is systematically investigated. The results indicate that benzo[b]thiophene is a promising electron donor for organic dyes. With a cone-shaped electron donor, these dyes possess an attractively broad photo-response ranging but shows relatively lower short-circuit photocurrent density than that of the reference dye WR7 (a rod-shaped dye). The origin of photocurrent limitation has been investigated in terms of electron injection, dye regeneration and interfacial charge recombination, with the latter found to be the governing factor. The present result shows that molecules able to control the charge recombination in DSSCs would be structures of interest in the design of highly efficient phenothiazine dyes.

Design and Application of an Optical Sensor for Simultaneous Imaging of pH and Dissolved O2 with Low Cross-Talk

Visualization and quantification of analytes such as O2 or pH is essential in biological research. Here we present the design and application of a new optical dual-analyte sensor for imaging, optimized to have low cross-sensitivity between the two analytes O2 and pH. The used indicator and reference dyes were selected to match the different channels of a commercial 2CCD (RGB + NIR) camera. A red-light emitting O2-sensitive europium complex (Eu(HPhN)3dpp) with a dynamic range of 0–20% O2 in the finished sensor was combined with a near-infrared emitting pH indicator (OHButoxy-aza-BODIPY) with a dynamic range of pH 7.2–8.8. To enable ratiometric readout, an inert reference coumarin dye (Bu3Coum) was co-immobilized with the optical indicators. In order to maximize the sensor signal, inert diamond powder was added to one sensor layer as a simple way to increase scattering of light within the sensor. Furthermore, the addition of an optical isolation layer enabled measurements in highly fluorescent samples, such...

Quantitative generalized ratiometric fluorescence spectroscopy for turbid media based on probe encapsulated by biologically localized embedding

PEBBLE (probe encapsulated by biologically localized embedding) nanosensor encapsulating an intensity-based fluorescence indicator and an inert reference fluorescence dye inside the pores of stable matrix can be used as a generalized wavelength-ratiometric probe. However, the lack of an efficient quantitative model render the choices of inert reference dyes and intensity-based fluorescence indicators used in PEBBLEs based generalized wavelength-ratiometric probes rather limited. In this contribution, an extended quantitative fluorescence model was derived specifically for generalized wavelength-ratiometric probes based on PEBBLE technique (QFMGRP) with a view to simplify the design of PEBBLEs and hence further extend their application potentials. The effectiveness of QFMGRP has been tested on the quantitative determination of free Ca2+ in both simulated and real turbid media using a Ca2+ sensitive PEBBLE nanosensor encapsulating Rhod-2 and eosin B inside the micropores of stable polyacrylamide matrix. Experimental results demonstrated that QFMGRP could realize precise and accurate quantification of free Ca2+ in turbid samples, even though there is serious overlapping between the fluorescence excitation peaks of eosin B and Ca2+ bound Rhod-2. The average relative predictive error value of QFMGRP for the test simulated turbid samples was 5.9%, about 2–4 times lower than the corresponding values of partial least squares calibration model and the empirical ratiometric model based on the ratio of fluorescence intensities at the excitation peaks of Ca2+ bound Rhod-2 and eosin B. The recovery rates of QFMGRP for the real and spiked turbid samples varied from 93.1% to 101%, comparable to the corresponding results of atomic absorption spectrometry.

New AB2 type two-photon absorption dyes for well-separated dual-emission: molecular preorganization based approach to photophysical properties

A variety of AB2 type new target dyes containing two proton transfer segments (o-hydroxy-phenyl-imino) are presented in this study. Furthermore, the corresponding reference molecules absent of hydroxy or imino groups are provided as well. Dual intramolecular hydrogen bonds in the target dyes are demonstrated by 1H NMR spectra, X-ray single crystal analysis as well as one-photon absorption spectra. Linear emission properties (static and transient emission nature) and two-photon absorption optical properties of these target and reference dyes are determined in various media such as organic solvents, solid phase state as well as PMMA substrate. The results show that the new AB2 type target dyes can efficiently undergo internal proton transfer in the excited states under one-photon irradiation and near-infrared femtosecond laser two-photon irradiation, respectively, and thus they exhibit well-separated dual-emission. The molecular geometry optimization is performed for the analysis of the occurrence of internal proton transfer in the excited states of the target AB2 chromophores.

Self-Assembled Fluorescent Bovine Serum Albumin Nanoprobes for Ratiometric pH Measurement inside Living Cells.

In this work, we demonstrated a new ratiometric method for the quantitative analysis of pH inside living cells. The structure of the nanosensor comprises a biofriendly fluorescent bovine serum albumin (BSA) matrix, acting as a pH probe, and pH-insensitive reference dye Alexa 594 enabling ratiometric quantitative pH measurement. The fluorescent BSA matrix was synthesized by cross-linking of the denatured BSA proteins in ethanol with glutaraldehyde. The size of the as-synthesized BSA nanoparticles can be readily manipulated from 30 to 90 nm, which exhibit decent fluorescence at the peak wavelength of 535 nm with a pH response range of 6-8. The potential of this pH sensor for intracellular pH monitoring was demonstrated inside living HeLa cells, whereby a significant change in fluorescence ratio was observed when the pH of the cell was switched from normal to acidic with anticancer drug treatment. The fast response of the nanosensor makes it a very powerful tool in monitoring the processes occurring within the cytosol.

Colour removal using nanoparticles

Nickel nanoparticles were synthesized and used to decolourize dye effluent. C. I. Reactive Blue 21 was taken as a reference dye, and polyvinyl pyrrolidone (PVP) was used as a stabilizer to prevent agglomeration of nanoparticles. Characterization of nanoparticles was done by a laser light scattering particle size analyzer, X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). Various parameters like pH, dye concentration, nanoparticle concentration, alkali addition, salt addition and duration studied for dye decolourization. To confirm the attachment of degraded products of dye on the nanoparticles, FT-IR analysis was done. About 98 % colour removal with simultaneous reduction in chemical oxygen demand (COD) was achieved.

FITC Doped Rattle-Type Silica Colloidal Particle-Based Ratiometric Fluorescent Sensor for Biosensing and Imaging of Superoxide Anion.

Fluorescent nanosensors have been widely applied in recognition and imaging of bioactive small molecules; however, the complicated surface modification process and background interference limit their applications in practical biological samples. Here, a simple, universal method was developed for ratiometric fluorescent determination of general small molecules. Taking superoxide anion (O2(•-)) as an example, the designed sensor was composed of three main moieties: probe carrier, rattle-type silica colloidal particles (mSiO2@hmSiO2 NPs); reference fluorophore doped into the core of NPs, fluorescein isothiocyanate (FITC); fluorescent probe for superoxide anion, hydroethidine (HE). In the absence of O2(•-), the sensor just emitted green fluorescence of FITC at 518 nm. When released HE was oxidized by O2(•-), the oxidation product exhibited red fluorescence at 570 nm and the intensity was linearly associated with the concentration of O2(•-), while that of reference element remained constant. Accordingly, ratiometric determination of O2(•-) was sensitively and selectively achieved with a linear range of 0.2-20 μM, and the detection limit was calculated as low as 80 nM. Besides, the technique was also successfully applied for dual-emission imaging of O2(•-) in live cells and realized visual recognition with obvious fluorescence color change in normal conditions or under oxidative stress. As long as appropriate reference dyes and sensing probes are selected, ratiometric biosensing and imaging of bioactive small molecules would be achieved. Therefore, the design could provide a simple, accurate, universal platform for biological applications.

Development of dual-emission ratiometric probe-based on fluorescent silica nanoparticle and CdTe quantum dots for determination of glucose in beverages and human body fluids

A novel dual emission ratiometric fluorescence probe for determination of glucose has been developed. The reference dye fluorescence isothiocyanate (FITC) has been encapsulated in the silica nanoparticles and then the red emission CdTe QDs were grafted on the surface of the silica particles to obtain the fluorescence probe. With glucose and dopamine as substrates, the glucose level was proportional to the fluorescence ratio change of above probe caused by dopamine oxidation, which was produced via bienzyme catalysis (glucose oxidase and horseradish peroxidase). The established approach was sensitive and selective, and has been applied to determine the glucose in beverage, urine and serum samples. The average recoveries of the glucose at various spiking levels ranged from 95.5% to 108.9% with relative standard deviations from 1.5% to 4.3%. The results provided a clue to develop sensors for rapid determination of the target analytes from complex matrices.

Theoretical design of coumarin derivatives incorporating auxiliary acceptor with D-π-A-π-A configuration for dye-sensitized solar cells

Abstract This study investigated the effects of incorporating benzothiadiazole (BTD) on the geometrical, photophysical, and electronic properties of coumarin-based dyes. New D-A-π-A and D-π-A-π-A systems arise from the presence of a BTD substituent, and we compare the properties these emergent systems to those of the pristine D-π-A system. The dyes were investigated on a theoretical basis using density functional theory (DFT) and time-dependent DFT methods. The new D-A-π -A and D-π-A-π-A structures have lower energy LUMOs and smaller energy gaps than the pristine dyes, resulting in significantly red-shifted absorption spectra. The substituted dyes may have application in improved light-harvesting ability. The delocalised ring systems present on BTD increase charge-transfer distances and provide a greater dipole moment, resulting in improvements to charge transfer properties over those of the unmodified dye. Additionally, D-π-A-π-A configuration shows efficiently electron injection from dye to TiO 2 . Compared with NKX-2510 reference dye, the absorption spectra of NCTBTA on TiO 2 surface exhibits a red shift up to 123 nm indicates remarkably stronger intramolecular charge transfer (ICT) and greatly improved electron injection efficiency. Our findings provide valuable information for the design of novel organic sensitizers for highly-efficient dye-sensitized solar cells.