Dynamics of Fluorescent Dyes Attached to G‐Quadruplex DNA and their Effect on FRET Experiments

FRET spectroscopy is a promising approach for investigating the dynamics of G‐quadruplex DNA folds and improving the targeting of G‐quadruplexes by potential anticancer compounds. To better interpret such experiments, classical and replica‐exchange molecular dynamics simulations and fluorescence‐lifetime measurements are used to understand the behavior of a range of Cy3‐based dyes attached to the 3′ end of G‐quadruplex DNA. The simulations revealed that the dyes interact extensively with the G‐quadruplex. Identification of preferred dye positions relative to the G‐quadruplex in the simulations allows the impact of dye–DNA interactions on FRET results to be determined. All the dyes show significant deviations from the common approximation of being freely rotating and not interacting with the host, but one of the Cy3 dye analogues is slightly closer to this case.     

Application of a Highly Robust and Efficient Fluorescence‐Resonance‐Energy‐Transfer (FRET) System in DNA

We report a feasibility study for the application of our newly developed highly efficient and robust fluorescence‐resonance‐energy‐transfer (FRET) system to DNA. A 2′‐oligodeoxynucleotide, 12 , equipped with a quinolinone derivative as donor and a (bathophenanthroline)ruthenium(II) complex as acceptor and having a single uridine as potential cleavage site under basic conditions revealed an intensive FRET, which almost vanished after cleavage of the oligonucleotide under basic conditions (Fig. 7). Furthermore, in the arrangement of a molecular beacon (MB) DNA (see 13 ), a significant decrease of the FRET was observed after hybridization to a target sequence (Fig. 9). Due to the long decay times of the fluorescence of the Ru‐complex, the system allows for highly sensitive time‐gated measurements.     

A New Robust and Highly Sensitive FRET Donor–Acceptor Pair: Synthesis,Characterization, and Application in a Thrombin Assay

The synthesis of a new, robust fluorescence‐resonance‐energy‐transfer (FRET) system is described. Its donor chromophore is derived from an N‐allyl‐substituted quinolinone attached to 4‐bromophenylalanine via Heck cross‐coupling. The resulting Fmoc‐protected derivative 11 was used as building block in solid‐phase peptide synthesis (SPPS). As FRET acceptor, a sulfonylated ruthenium(II)–bathophenanthroline complex with a peripheral COOH function was prepared for covalent attachment to target molecules. The UV/VIS absorption and emission spectra of peptides bearing only the donor (D) or acceptor (A) dye showed a good overlap of the emission band of the donor with the absorption band of the acceptor. The fluorescence spectra of a peptide bearing both dyes revealed an additional emission after excitation of the donor, which is due to indirect excitation of the acceptor via FRET. The long fluorescence lifetime of the Ru^II complex (0.53 μs) makes it well‐suited for time‐resolved measurements. As a first application of this new FRET system, the peptide 18 , with the recognition sequence for the protease thrombin, flanked by the two dyes, was synthesized and successfully cleaved by the enzyme. The change in the ratio of the fluorescence intensities could be determined.     

Core‐Shell Structured Layered Lanthanide‐Organic Complexes with Stilbazolium‐type Dye Encapsulation for Multifunctional Performances

Host‐guest encapsulation of functional organic dye into a porous metal‐organic framework can give rise to the development of new functional materials. In this work, by intercalating the stilbazolium‐type dye (DEAST)I (4′‐diethylamino‐N‐methyl stilbazolium) into four lanthanide layered metal‐organic complexes (Ln‐LMOCs), i. e. {[Ln(BTB)(H₂O)₂]?3(DMF)?2(H₂O)}_n (Ln=La (1), Nd (2), Sm (3), Er (4)), four responsive (DEAST)I@Ln‐LMOC composites have been prepared, serving as multifunctional performance platform. The core–shell structures of (DEAST)I@Ln‐LMOC composites have been fully characterized by IR, UV/Vis, PXRD, SEM, TEM, TGA and ESR. Significantly, after intercalation of dyes, the (DEAST)I@Ln‐LMOC composites exhibit enhanced luminescent sensing properties in detecting Fe³⁺ with much higher water stabilities. The luminescent sensing behavior stems from the fluorescence resonance energy transfer (FRET) from the π‐electron‐rich BTB ligands to the Fe³⁺, and their higher water stabilities are induced by electrostatic interactions and lower porosity. Specially, the characteristic emissions of Sm³⁺ will not be affected after the encapsulation guest dyes, which provide a theoretical guide for the modulation of luminescence devices. Finally, better ion conductivities and diminished photocurrents can be achieved after the embedding of the functional organic dye. In all, the formation of (DEAST)I@Ln‐LMOC composites with core–shell structures can be utilized as a multifunctional platform with good stability.     

Programmed Synthesis by Stimuli‐Responsive DNAzyme‐Modified Mesoporous SiO2 Nanoparticles

DNAzyme‐capped mesoporous SiO₂ nanoparticles (MP SiO₂ NPs) are applied as stimuli‐responsive containers for programmed synthesis. Three types of MP SiO₂ NPs are prepared by loading the NPs with Cy3‐DBCO (DBCO=dibenzocyclooctyl), Cy5‐N₃, and Cy7‐N₃, and capping the NP containers with the Mg²⁺, Zn²⁺, and histidine‐dependent DNAzyme sequences, respectively. In the presence of Mg²⁺ and Zn²⁺ ions as triggers, the respective DNAzyme‐capped NPs are unlocked, leading to the “click” reaction product Cy3‐Cy5. In turn, in the presence of Mg²⁺ ions and histidine as triggers the second set of DNAzyme‐capped NPs is unlocked leading to the Cy3‐Cy7 conjugated product. The unloading of the respective NPs and the time‐dependent formation of the products are followed by fluorescence spectroscopy (FRET). A detailed kinetic model for the formation of the different products is formulated and it correlates nicely with the experimental results.     

Synthesis and Spectroscopic Characterization of Fluorophore‐Labeled Oligospiroketal Rods

Fluorescence probes consisting of well‐established fluorophores in combination with rigid molecular rods based on spirane‐type structures were investigated with respect to their fluorescence properties under different solvent conditions. The attachment of the dyes was accomplished by 1,3‐dipolar cycloaddition between alkynes and azides (‘click’ reaction) and is a prime example for a novel class of sensor constructs. Especially, the attachment of two (different) fluorophores on opposite sides of the molecular rods paves the way to new sensor systems with less bulky (compared to the conventional DNA‐ or protein‐based concepts), nevertheless rigid spacer constructs, e.g., for FRET‐based sensing applications. A detailed photophysical characterization was performed in MeOH (and in basic H₂O/MeOH mixtures) for i) rod constructs containing carboxyfluorescein, ii) rod constructs containing carboxyrhodamine, iii) rod constructs containing both carboxyfluorescein and carboxyrhodamine, and iv) rod constructs containing both pyrene and perylene parts. For each dye (pair), two rod lengths with different numbers of spirane units were synthesized and investigated. The rod constructs were characterized in ensemble as well as single‐molecule fluorescence experiments with respect to i) specific rod? dye and ii) dye? dye interactions. In addition to MeOH and MeOH/NaOH, the rod constructs were also investigated in micellar systems, which were chosen as a simplified model for membranes.     

Photophysical Properties of 7‐(diethylamino)Coumarin‐3‐carboxylic Acid in the Nanocage of Cyclodextrins and in Different Solvents and Solvent Mixtures

The photophysical properties of 7‐(diethylamino) coumarin‐3‐carboxylic acid (7‐DCCA) were studied in cyclodextrins (α, β, γ,‐CDs), different neat solvents and solvent mixtures by using steady state absorption, emission and time‐resolved fluorescence spectroscopy. We have observed that with gradual increase in concentration of β‐CD the fluorescence quantum yield and lifetime decreased in a regular pattern whereas with gradual increase in concentration of γ‐CD the fluorescence quantum yield and lifetime gradually increased. With addition of urea, the fluorescence quantum yield and lifetime of 7‐DCCA in CDs increased. Binding constant calculation shows that 7‐DDCA forms 1:1 complex with β‐CD and with γ‐CD it forms 1:1 and 1:2 (guest:host) inclusion complex. We proposed that the dye molecule formed capping complex with β‐CD by means of hydrogen bonding and after addition of urea the hydrogen bonding network broke down and part of dye molecule entered inside the cavity of β‐CD. The photophysics of 7‐DCCA was studied in dioxane‐water mixture and ethylene glycol‐acetonitrile mixture to know the effect of polarity and viscosity of the media. The photophysics of 7‐DCCA was also studied in different neat solvents. It was found that the photophysics of 7‐DCCA depended on the structural feature of the solvents and solvent mixtures.     

Efficient Excitation‐Energy Transfer in Ion‐Based Organic Nanoparticles with Versatile Tunability of the Fluorescence Colours

Organic nanoparticles consisting of 3,3′‐diethylthiacyanine (TC) and ethidium (ETD) dyes are synthesized by ion‐association between the cationic dye mixture (10 % ETD doping) and the tetrakis(4‐fluorophenyl)borate (TFPB) anion, in the presence of a neutral stabilizing polymer, in aqueous solution. Doping with ETD makes the particle size smaller than without doping. Size tuning can also be conducted by varying the molar ratio (ρ) of the loaded anion to the cationic dyes. The fluorescence spectrum of TC shows good overlap with the absorption of ETD in the 450–600 nm wavelength region, so efficient excitation‐energy transfer from TC (donor) to ETD (acceptor) is observed, yielding organic nanoparticles whose fluorescence colours are tunable. Upon ETD doping, the emission colour changes significantly from greenish‐blue to reddish or whitish. This change is mainly dependent on ρ. For the doped nanoparticle sample with ρ=1, the intensity of fluorescence ascribed to ETD is ～150‐fold higher than that from pure ETD nanoparticles (efficient antenna effect). Non‐radiative Förster resonance‐energy transfer (FRET) is the dominant mechanism for the ETD fluorescence enhancement. The organic nanoparticles of a binary dye system fabricated by the ion‐association method act as efficient light‐harvesting antennae, which are capable of transferring light energy to the dopant acceptors in very close proximity to the donors, and can have multi‐wavelength emission colours with high fluorescence quantum yields.     

From Dark to Light to Fluorescence Resonance Energy Transfer (FRET): Polarity‐Sensitive Aggregation‐Induced Emission (AIE)‐Active Tetraphenylethene‐Fused BODIPY Dyes with a Very Large Pseudo‐Stokes Shift

The work presented herein is devoted to the fabrication of large Stokes shift dyes in both organic and aqueous media by combining dark resonance energy transfer (DRET) and fluorescence resonance energy transfer (FRET) in one donor–acceptor system. In this respect, a series of donor–acceptor architectures of 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) dyes substituted by one, two, or three tetraphenylethene (TPE) luminogens were designed and synthesised. The photophysical properties of these three chromophore systems were studied to provide insight into the nature of donor–acceptor interactions in both THF and aqueous media. Because the generation of emissive TPE donor(s) is strongly polarity dependent, due to its aggregation‐induced emission (AIE) feature, one might expect the formation of appreciable fluorescence emission intensity with a very large pseudo‐Stokes shift in aqueous media when considering FRET process. Interestingly, similar results were also recorded in THF for the chromophore systems, although the TPE fragment(s) of the dyes are non‐emissive. The explanation for this photophysical behaviour lies in the DRET. This is the first report on combining two energy‐transfer processes, namely, FRET and DRET, in one polarity‐sensitive donor–acceptor pair system. The accuracy of the dark‐emissive donor property of the TPE luminogen is also presented for the first time as a new feature for AIE phenomena.     

High‐Performance Förster Resonance Energy Transfer (FRET)‐Based Dye‐Sensitized Solar Cells: Rational Design of Quantum Dots for Wide Solar‐Spectrum Utilization

High‐performance Förster resonance energy transfer (FRET)‐based dye‐sensitized solar cells (DSSCs) have been successfully fabricated through the optimized design of a CdSe/CdS quantum‐dot (QD) donor and a dye acceptor. This simple approach enables quantum dots and dyes to simultaneously utilize the wide solar spectrum, thereby resulting in high conversion efficiency over a wide wavelength range. In addition, major parameters that affect the FRET interaction between donor and acceptor have been investigated including the fluorescent emission spectrum of QD, and the content of deposited QDs into the TiO₂ matrix. By judicious control of these parameters, the FRET interaction can be readily optimized for high photovoltaic performance. In addition, the as‐synthesized water‐soluble quantum dots were highly dispersed in a nanoporous TiO₂ matrix, thereby resulting in excellent contact between donors and acceptors. Importantly, high‐performance FRET‐based DSSCs can be prepared without any infrared (IR) dye synthetic procedures. This novel strategy offers great potential for applications of dye‐sensitized solar cells.     

A Promising Candidate with D‐A‐A‐A Architecture as an Efficient Sensitizer for Dye‐Sensitized Solar Cells

A series of metal‐free organic dyes with electron‐rich (D) and electron‐deficient units (A) as π linkers have been studied theoretically by means of density functional theory (DFT) and time‐dependent DFT calculations to explore the effects of π spacers on the optical and electronic properties of triphenylamine dyes. The results show that Dye 1 with a structure of D‐A‐A‐A is superior to the typical C218 dye in various key aspects, including the maximum absorption (λ_max=511 nm), the charge‐transfer characteristics (D/Δq/t is 5.49 Å/0.818 e^?/4.41 Å), the driving force for charge‐carrier injection (ΔG_inject=1.35 eV)/dye regeneration (ΔG_regen=0.27 eV), and the lifetime of the first excited state (τ=3.1 ns). It is thus proposed to be a promising candidate in dye‐sensitized solar cell applications.     

Efficient NIR‐Light Emission from Solid‐State Complexes of Boron Difluoride with 2′‐Hydroxychalcone Derivatives

This article describes a series of nine complexes of boron difluoride with 2′‐hydroxychacone derivatives. These dyes were synthesized very simply and exhibited intense NIR emission in the solid state. Complexation with boron was shown to impart very strong donor–acceptor character into the excited state of these dyes, which further shifted their emission towards the NIR region (up to 855 nm for dye 5 b , which contained the strongly donating triphenylamine group). Strikingly, these optical features were obtained for crystalline solids, which are characterized by high molecular order and tight packing, two features that are conventionally believed to be detrimental to luminescence in organic crystals. Remarkably, the emission of light from the π‐stacked molecules did not occur at the expense of the emission quantum yield. Indeed, in the case of pyrene‐containing dye 4 , for example, a fluorescence quantum yield of about 15 % with a fluorescence emission maximum at 755 nm were obtained in the solid state. Moreover, dye 3 a and acetonaphthone‐based compounds 1 b , 2 b , and 3 b showed no evidence of degradation as solutions in CH₂Cl₂ that contained EtOH. In particular, solutions of brightly fluorescent compound 3 a (brightness: ε×Φ_f=45 000 M ^?1 cm^?1) could be stored for long periods without any detectable changes in its optical properties. All together, these new dyes possess a set of very interesting properties that make them promising solid‐state NIR fluorophores for applications in materials science.     

Molecular‐Recognition‐Assisted pKa Shifts and Metal‐Ion‐Induced Fluorescence Regeneration in p‐Sulfonatocalix[6]arene‐Encapsulated Acridine

The host–guest interactions of cationic (AcH⁺) and neutral (Ac) forms of the dye acridine with the macrocyclic host p‐sulfonatocalix[6]arene (SCX6) were investigated by using ground‐state absorption, steady‐state and time‐resolved fluorescence, and NMR measurements. The cationic form undergoes significant complexation with SCX6 (K_eq=2.5×10⁴ M ^?1), causing a sharp decrease in the fluorescence intensity and severe quenching in the excited‐state lifetime of the dye. The strong binding of the AcH⁺ form of the dye with SCX6 is attributed to ion–ion interactions involving the sulfonato groups (SO₃^?) of SCX6 and the positively charged AcH⁺ at pH of approximately 4.3. Whereas, the neutral Ac form of the dye undergoes weak complexation with SCX6 (K_eq=0.9×10³ M ^?1) and the binding constant is lowered by one order of magnitude compared with that of the SCX6–AcH⁺ system. The strong affinity of SCX6 to the protonated form leads to a large upward pK_a shift (≈2 units) in the dye. In contrast, strong emission quenching upon SCX6 interaction and the regeneration of fluorescence intensity of the dye in the presence of Gd³⁺ through competitive binding have also been demonstrated.     

Design and characterization of two-dye and three-dye binary fluorescent probes for mRNA detection

We report the design, synthesis, and characterization of binary oligonucleotide probes for mRNA detection. The probes were designed to avoid common problems found in standard binary probes such as direct excitation of the acceptor fluorophore and overlap between the donor and acceptor emission spectra. Two different probes were constructed that contained an array of either two or three dyes and were characterized using steady-state fluorescence spectroscopy, time-resolved fluorescence spectroscopy, and fluorescence depolarization measurements. The three-dye binary probe (BP-3d) consists of a Fam fluorophore which acts as a donor, collecting light and transferring it as energy to Tamra, which subsequently transfers energy to Cy5 when the two probes are hybridized to mRNA. This design allows the use of 488 nm excitation, which avoids the direct excitation of Cy5 and at the same time provides a good fluorescence resonance energy transfer (FRET) efficiency. The two-dye binary probe system (BP-2d) was constructed with Alexa488 and Cy5 fluorophores. Although the overlap between the fluorescence of Alexa488 and the absorption of Cy5 is relatively low, FRET still occurs due to their close physical proximity when the probes are hybridized to mRNA. This framework also decreases the direct excitation of Cy5 and reduces the fluorescence overlap between the donor and the acceptor. Picosecond time-resolved spectroscopy showed a reduction in the fluorescence lifetime of donor fluorophores after the formation of the hybrid between the probes and target mRNA. Interestingly, BP-2d in the presence of mRNA shows a slow rise in the fluorescence decay of Cy5 due to a relatively slow FRET rate, which together with the reduction in the Alexa488 lifetime provides a way to improve the signal to background ratio using time-resolved fluorescence spectra (TRES). In addition, fluorescence depolarization measurements showed complete depolarization of the acceptor dyes (Cy5) for both BP-3d (due to sequential FRET steps) and BP-2d (due to the relatively low FRET rate) in the presence of the mRNA target.     

Förster resonance energy transfer in poly(methyl methacrylates) copolymers bearing donor–acceptor 1,3‐thiazole dyes

The Förster resonance energy transfer (FRET) properties in poly(methyl methacrylate) copolymers containing 2‐(pyridine‐2‐yl) thiazole dyes were studied upon systematic variation of the donor‐to‐acceptor ratio. To this end, 2‐(pyridine‐2‐yl) thiazole dyes specially designed for the usage as energy donor and acceptor molecules were incorporated within one polymer chain. Poly(methyl methacrylate) copolymers containing these donor and acceptor dyes were synthesized using the RAFT polymerization method. Copolymers with a molar mass (M_n) of nearly 10,000 g/mol were achieved with dispersity index values (?) under 1.3. The presented copolymers act as a model system for the FRET investigation. Förster resonance energy transfer properties of the copolymers are characterized by steady state as well as time resolved fluorescence spectroscopy. The results indicate that the energy transfer rates and the transfer efficiencies are tunable by variation of the donor‐acceptor‐ratio. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4765–4773     

Bi‐anchoring Organic Dyes that Contain Benzimidazole Branches for Dye‐Sensitized Solar Cells: Effects of π Spacer and Peripheral Donor Groups

Benzimidazole‐branched bi‐anchoring organic dyes that contained triphenylamine/phenothiazine donors, 2‐cyanoacrylic acid acceptors, and various π linkers were synthesized and examined as sensitizers for dye‐sensitized solar cells. The structure–activity relationships in these dyes were systematically investigated by using absorption spectroscopy, cyclic voltammetry, and density functional theory calculations. The wavelength of the absorption peak was more‐heavily influenced by the nature of the π linker than by the nature of the donor. For a given donor, the absorption maximum (λ_max) was red‐shifted on changing the π linker from phenyl to 2,2′‐bithiophene, whilst the dyes that contained triphenylamine units displayed higher molar extinction coefficients (?) than their analogous phenothiazine‐based triphenylamine dyes, which led to good light‐harvesting properties in the triphenylamine‐based dyes. Electrochemical data for the dyes indicated that the triphenylamine‐based dyes possessed relatively low‐lying HOMOs, which could be beneficial for suppressing back electron transfer from the conduction band of TiO₂ to the oxidized dyes, owing to facile regeneration of the oxidized dye by the electrolyte. The best performance in the DSSCs was observed for a dye that possessed a triphenylamine donor and 2,2′‐bithiophene π linkers. Electron impedance spectroscopy (EIS) studies revealed that the use of triphenylamine as the donor and phenyl or 2,2′‐bithiophene as the π linkers was beneficial for disrupting the dark current and charge‐recombination kinetics, which led to a long electron lifetime of the injected electrons in the conduction band of TiO₂.     

Pyrazole‐substituted Near‐infrared Cyanine Dyes Exhibit pH‐dependent Fluorescence Lifetime Properties

Near‐infrared heptamethine cyanine dye is functionalized with pyrazole derivatives at the meso‐position to induce pH‐dependent photophysical properties. The presence of pyrazole unsubstituted at ¹N‐position is essential to induce pH‐dependent fluorescence intensity and lifetime changes in these dyes. Replacement of meso‐chloro group of cyanine dye IR820 with ¹N‐unsubstituted pyrazole resulted in the pH‐dependent fluorescence lifetime changes from 0.93 ns in neutral media to 1.27 ns in acidic media in DMSO. Time‐resolved emission spectra (TRES) revealed that at lower pH, the pyrazole consists of fluorophores with two distinct lifetimes, which cor‐responds to pH‐sensitive and non‐pH‐sensitive species. In contrast, ¹N‐substituted pyrazoles do not exhibit pH response, suggesting excited state electron transfer as the mechanism of pH‐dependent fluorescence lifetime sensitivity for this class of compounds.     

A Novel Route to 1‐Substituted 3‐(Dialkylamino)‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles

Heptalenecarbaldehydes 1 / 1′ as well as aromatic aldehydes react with 3‐(dicyanomethylidene)‐indan‐1‐one in boiling EtOH and in the presence of secondary amines to yield 3‐(dialkylamino)‐1,2‐dihydro‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles (Schemes 2 and 4, and Fig. 1). The 1,2‐dihydro forms can be dehydrogenated easily with KMnO₄ in acetone at 0° (Scheme 3) or chloranil (=2,3,5,6‐tetrachlorocyclohexa‐2,5‐diene‐1,4‐dione) in a ‘one‐pot’ reaction in dioxane at ambient temperature (Table 1). The structures of the indeno[2,1‐c]pyridine‐4‐carbonitriles 5′ and 6a have been verified by X‐ray crystal‐structure analyses (Fig. 2 and 4). The inherent merocyanine system of the dihydro forms results in a broad absorption band in the range of 515–530 nm in their UV/VIS spectra (Table 2 and Fig. 3). The dehydrogenated compounds 5, 5′ , and 7a – 7f exhibit their longest‐wavelength absorption maximum at ca. 380 nm (Table 2). In contrast to 5 and 5′, 7a – 7f in solution exhibit a blue‐green fluorescence with emission bands at around 460 and 480 nm (Table 4 and Fig. 5).     

Dye‐Sensitized Solar Cells Based on a Donor–Acceptor System with a Pyridine Cation as an Electron‐Withdrawing Anchoring Group

New hemicyanine dyes ( CM101 , CM102 , CM103 , and CM104 ) in which tetrahydroquinoline derivatives are used as electron donors and N‐(carboxymethyl)‐pyridinium is used as an electron acceptor and anchoring group were designed and synthesized for dye‐sensitized solar cells (DSSCs). Compared with corresponding dyes that have cyanoacetic acid as the acceptor, N‐(carboxymethyl)‐pyridinium has a stronger electron‐withdrawing ability, which causes the absorption maximum of dyes to be redshifted. The photovoltaic performance of the DSSCs based on dyes CM101 – CM104 markedly depends on the molecular structures of the dyes in terms of the n‐hexyl chains and methoxyl. The device sensitized by dye CM104 achieved the best conversion efficiency of 7.0 % (J_sc=13.4 mA cm^?2, V_oc=704 mV, FF=74.8 %) under AM 1.5 irradiation (100 mW cm^?2). In contrast, the device sensitized by reference dye CMR104 with the same donor but the cyanoacetic acid as the acceptor gave an efficiency of 3.4 % (J_sc=6.2 mA cm^?2, V_oc=730 mV, FF=74.8 %). Under the same conditions, the cell fabricated with N719 sensitized porous TiO₂ exhibited an efficiency of 7.9 % (J_sc=15.4 mA cm^?2, V_oc=723 mV, FF=72.3 %). The dyes CM101 – CM104 show a broader spectral response compared with the reference dyes CMR101 – CMR104 and have high IPCE exceeding 90 % from 450 to 580 nm. Considering the reflection of sunlight, the photoelectric conversion efficiency could be almost 100 % during this region.     

Theoretical studies on triaryamine‐based p‐type D‐D‐π‐A sensitizer

Development of triaryamine‐based nonmetallic dye sensitizers is a hot topic in the solar cell research. A series of triaryamine‐based dyes WS1 – WS7 were designed with W1 as the prototype. Density functional theory (DFT) and time‐dependent‐DFT calculations were used to investigate the effects of the attached donor D on the absorption spectra and electronic properties of the dyes. The light‐harvesting efficiency (LHE), hole injection force (ΔG_inj), dye regeneration force (ΔG_reg), and charge recombination force (ΔG_CR) for all the dyes were predicted. The insertion of D not only results in a red shift in the absorption spectra for all dyes but also achieves a broader absorption for visible light. Compared with that of the prototype, the absorption peak of the dye WS7 has a red shift of 95 nm and an oscillator strength increase of 29%. The absorption peak of WS7 is wider and stronger, and the absorption range extends to 900 nm. The LHE and ΔG_reg values of WS7 are 0.991 and ?1.49 eV, respectively. On overall evaluation, WS7 is a promising candidate of a p‐type dye sensitizer with good light absorption and dye regeneration efficiency.