Excitation-Wavelength-Dependent Charge Injection and Hole Localization in Diblock Oligomers Anchored to TiO2

A series of diblock oligomers containing oligothiophene (Tn, n = 4, 5) and 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadizole (TBT) segments, functionalized with carboxylic acid anchoring groups, were prepared and anchored to mesoporous TiO2 films to study wavelength-dependent interfacial electron transfer mechanisms. Thin films of the surface-anchored diblock oligomers contained two absorption bands centered at 400 and 500 nm, corresponding to the Tn and TBT blocks, respectively. Pulsed-laser excitation of the oligomer-sensitized films yielded local excited-states that promoted electron injection into TiO2. The injection pathway was dependent on the excitation wavelength, as electron injection occurred from the oligomer block that was locally excited. Recombination between the injected electron and the oxidized oligomer was sensitive to the bridging unit that separates the oligomer conjugated segments (-C≡C- vs trans-Pt(PBu3)2-). When the bridge facilitated strong coupling between the two blocks (-C≡C- bridge), the excitation wavelength had no effect on the recombination pathway, as the hole was delocalized over the entire oligomer. However, in the weak coupling case (Pt(PBu3)2- bridge), selective excitation resulted in wavelength-dependent hole localization that persisted to the μs time scale, providing control over the recombination pathway by varying the excitation wavelength. Dye-sensitized solar cells (DSSCs) were fabricated by using the diblock oligomers as sensitizers. The photocurrent action spectra were measured, and the absorbed photon-to-current efficiency (APCE) provided further insight into the electron-transfer mechanisms that are operative under continuous illumination.

Organic-Inorganic Porphyrinoid Frameworks for Biomolecule Sensing

Porphyrinoids and their analogous compounds play an important role in biosensing applications on account of their unique and versatile catalytic, coordination, photophysical, and electrochemical properties. Their remarkable arrays of properties can be finely tuned by synthetically modifying the porphyrinoid ring and varying the various structural parameters such as peripheral functionalization, metal coordination, and covalent or physical conjugation with other organic or inorganic scaffolds such as nanoparticles, metal-organic frameworks, and polymers. Porphyrinoids and their organic-inorganic conjugates are not only used as responsive materials but also utilized for the immobilization and embedding of biomolecules for applications in wearable devices, fast sensing devices, and other functional materials. The present review delineates the impact of different porphyrinoid conjugates on their physicochemical properties and their specificity as biosensors in a range of applications. The newest porphyrinoid types and their synthesis, modification, and functionalization are presented along with their advantages and performance improvements.

Porphyrinatonickel(II)-Cyclopentene and Porphyrinatonickel(II)-Cyclopentadiene Hybrids: Zirconacyclopentadiene-Mediated Syntheses, Structures, and Mechanistic Study

The reaction of meso-formyl Ni(II) porphyrin 1 with zirconacyclopentadiene 2 in the presence of AlCl₃ afforded four products 3, 4, 5, and 6 with a total yield of over 85%. The structures of these compounds are well-characterized by ¹H NMR an d¹³C NMR spectroscopy, HRMS, and X-ray single-crystal diffraction. The mechanism is proposed mainly on the basis of isotopic labeling experiments, which showed that a Friedel-Crafts-type reaction and β-H shift may be critical during the formation of 5 and 6.

Photophysical and Computational Insights into Ag(I) Complexation of Porphyrinic Covalent Cages Equipped with Triazoles-Incorporating Linkers

The photophysical characterization of four supramolecular complexes based on covalent cages 2H-S-2H, 2H-L-2H, Zn-S-2H, and Zn-L-2H, consisting in either two free-base porphyrins or one Zn(II) porphyrin and one free-base porphyrin connected by four flexible linkers of different lengths incorporating triazole binding sites, and their Ag(I) complexation are reported. The complexation processes have been followed by means of absorption and emission spectroscopies, and a comprehensive computational study explains the behavior of the free-base porphyrin-containing cages. Absorption and emission features have been interpreted on the bases of conformational changes, metalation processes, and modification of energy transfer efficiencies occurring in the different cases. In all cages, except 2H-L-2H, the coordination of four Ag(I) ions to the lateral triazole groups of the linkers leads to the enlargement of their cavity. Only for 2H-L-2H is a different behavior observed, where the process of silver metalation of the porphyrins’ core prevails.

Complementary Photo-Synapses Based on Light-Stimulated Porphyrin-Coated Silicon Nanowires Field-Effect Transistors (LPSNFET)

Neuromorphic computing has emerged as the high-energy-efficiency and intelligent solution for processing sensory data. As a potential alternative to neuromorphic computing, photo-excited synaptic systems can integrate the functions of optoelectronic sensing and synaptic computing to realize the low-power and high-performance visual perception. However, one major challenge in high-efficient photo-excited synaptic system is to realize the complementarily enhanced and inhibited synaptic behaviors with small hardware cost as possible. Another challenge is to fabricate the photo-synapse devices with complementary metal oxide semiconductor (CMOS)-compatible process to achieve high enough integration density for practical application. Here, a CMOS-compatible Light-stimulated Porphyrin-coated Silicon Nanowire Field Effect Transistor (LPSNFET) technology is proposed and developed to form the complementary photo-synapses with only two CMOS-like transistors. LPSNFET exhibits fivefold improvement in photo-sensitivity compared to the bare silicon nanowire (SiNW) devices, and can still show obvious responses when incident illumination power is as low as 0.1 mW cm^-2 . Moreover, it enables tunable dynamic synaptic plasticity and versatile synaptic functions. Especially, the complementarily enhanced and inhibited behaviors can be realized by modulating SiNW/porphyrin interface via simply changing the MOS type of LPSNFET, which acts like the photonic counterpart of CMOS technology to provide the basic brick for building complex neuromorphic circuits efficiently and economically. Finally, the CMOS process compatibility of LPSNFET provides potential application in future large scale in-sensor computing.

Zinc porphyrin/mesoporous titania thin film electrodes: a hybrid material nanoarchitecture for photocatalytic reduction

In this work, photocatalytic reduction of methyl viologen is achieved using zinc tetra(4-N-methylpyridyl)porphine (ZnP) functionalized mesoporous titania thin films (MTTF). Also, ZnP sensitizing and photophysical properties are retained in the hybrid material.

The impact of insufficient time resolution on dye regeneration lifetime determined using transient absorption spectroscopy

Dye regeneration lifetimes of a combination of dyes and redox mediators were determined by two transient absorption (TA) spectrometers with 0.5 ns (sub-ns) and 6 ns (ns) time resolutions to elucidate the impact of insufficient time resolution on the measurements of dye regeneration kinetics in dye-sensitised semiconductor electrodes. Due to the disordered nature of the dye-sensitised electrodes, the dye regeneration lifetime is often characterised by half-decay time (τ1/2) of the initial signal magnitude. Alternatively, τ1/2,S is calculated from stretched-exponential lifetime (τww) and the distribution of lifetimes characterised by the stretch parameter (β). Stretched-exponential functions were numerically modelled, showing that to keep the error in τ1/2 ≤ 10%, τww needs to be at least 20 times longer than the time resolution in case of non-dispersive transients (β = 0.9) but at least 870 times longer when dispersive (β = 0.5). To test the predictions, TA decays of a combination of organic and porhyrin dyes and three cobalt-complex mediators are analysed, spanning a range of τww and β. These examples show that a 262% error in τ1/2 is possible if the time resolution of the TA setup is only 13 times faster than τww and smaller β results in larger error when τww is similar. Determining τ1/2,S by stretched-exponential fitting generally reduces the error compared to that determined directly from the graph. However, if the stretched-exponential function does not correctly describe the early signal transient, even a larger error by stretched-exponetial fitting is introduced. The key requirement for accurate measurement is to have a fast-enough TA setup to resolve the initial plateau of the TA signal. To demonstrate the impact of the measured errors, the measured regeneration lifetimes are plotted versus the driving force of the reaction and modelled using Marcus theory. Erroneous regeneration rates lead to an underestimated electronic coupling term by 2.2 times in case of a series of porphyrin dyes matched with Co complex electrolytes, a significant impact when the interpretation of factors affecting electron transfer at dye-sensitised semiconductor/electrolyte interface is discussed.

Theoretical analysis of the absorption spectrum, electronic structure, excitation, and intramolecular electron transfer of D-A'-π-A porphyrin dyes for dye-sensitized solar cells

A series of porphyrin dyes with D-A'-π-A structure were designed and theoretically investigated by DFT and TD-DFT methods. Different electron-withdrawing auxiliary acceptor units were introduced into the dye molecule skeleton to shed light on how the type and position of auxiliary acceptors influence the photoelectric performance of the dyes. It was found that the introduction of electron-withdrawing units, BTD, TPZ, BTZ, PP and DPPZ, between the Zn-porphyrin core and the anchoring group had a significantly positive influence on the performance of the dye molecules. Also, more appropriate electron distribution in the molecular orbital and the lower HOMO-LUMO energy gap, more extensive absorption coverage, higher light-harvesting efficiency, lower orbital overlap, and more effective long-range intramolecular electron transfer (IET) process can be achieved as compared to the reference dye. Among these five electron-withdrawing units, BTD and TPZ had the effect leading to the greatest improvement and therefore, are the best candidates for auxiliary acceptors. The calculated results indicated that the longitudinal π-conjugation of the electron-withdrawing unit also had an obvious effect on the performance of the dye molecule, and NTD is expected to be a more effective auxiliary acceptor than BTD. The effects of the relative positions of the auxiliary acceptors in the dye molecular skeleton were also investigated. A comparative study of AX1-3 and AA1-3 showed that the introduction of BTD, TPZ and BTZ units between the donor part and the Zn-porphyrin core may have a negative impact on the performance of the dyes. Our studies are expected to provide new insight for the design and screening of high-efficiency porphyrin dyes for DSSCs applications.

Regioselectivity of the 1,3-Dipolar Cycloaddition of Organic Azides to 7-Heteronorbornadienes. Synthesis of β-Substituted Furans/Pyrroles

An efficient procedure for the preparation of β-substituted furans/pyrroles is presented. The methodology is based on the use of 7-oxa/azanorbornadienes as dipolarophiles in 1,3-dipolar cycloaddition with benzyl azide. The triazoline cycloadduct thus formed spontaneously decomposes via a retro-Diels-Alder (rDA) reaction to afford a β-substituted furan/pyrrole derivative and a stable triazole. The scope of this tandem 1,3-dipolar cycloaddition/rDA reaction was studied with thirteen 7-heteronorbornadienes. This study allowed a deep knowledge of the regioselectivity of the reaction, which can be tuned through the substituents of the heteronorbornadienic systems.

Manipulating nanoscale structure to control functionality in printed organic photovoltaic, transistor and bioelectronic devices

Printed electronics is simultaneously one of the most intensely studied emerging research areas in science and technology and one of the fastest growing commercial markets in the world today. For the past decade the potential for organic electronic (OE) materials to revolutionize this printed electronics space has been widely promoted. Such conviction in the potential of these carbon-based semiconducting materials arises from their ability to be dissolved in solution, and thus the exciting possibility of simply printing a range of multifunctional devices onto flexible substrates at high speeds for very low cost using standard roll-to-roll printing techniques. However, the transition from promising laboratory innovations to large scale prototypes requires precise control of nanoscale material and device structure across large areas during printing fabrication. Maintaining this nanoscale material control during printing presents a significant new challenge that demands the coupling of OE materials and devices with clever nanoscience fabrication approaches that are adapted to the limited thermodynamic levers available. In this review we present an update on the strategies and capabilities that are required in order to manipulate the nanoscale structure of large area printed organic photovoltaic (OPV), transistor and bioelectronics devices in order to control their device functionality. This discussion covers a range of efforts to manipulate the electroactive ink materials and their nanostructured assembly into devices, and also device processing strategies to tune the nanoscale material properties and assembly routes through printing fabrication. The review finishes by highlighting progress in printed OE devices that provide a feedback loop between laboratory nanoscience innovations and their feasibility in adapting to large scale printing fabrication. The ability to control material properties on the nanoscale whilst simultaneously printing functional devices on the square metre scale is prompting innovative developments in the targeted nanoscience required for OPV, transistor and biofunctional devices.

Alkyl-Group-Wrapped Unsymmetrical Squaraine Dyes for Dye-Sensitized Solar Cells: Branched Alkyl Chains Modulate the Aggregation of Dyes and Charge Recombination Processes

Electron transfer processes at the interfaces dictate the factors that improve the photovoltaic parameters, such as open-circuit voltage (V_oc) and short-circuit current (J_sc), of a dye-sensitized solar cell device, besides selection of a set of suitable anode, dye, electrolyte, and cathode materials. An inefficient charge injection process at the dye-TiO₂ interface and charge recombination at the TiO₂-dye/electrolyte interface have detrimental effects on improving both J_sc and V_oc. Hence, tailoring the factors that govern the improvement of J_sc and V_oc will be an ideal approach to get the desired sensitizers with good device efficiencies. Squaraines are far-red-active zwitterionic dyes and have a high molar extinction coefficient along with unique aggregation properties due to the large dipole moment associated with them. Here, we report a series of unsymmetrical squaraine dyes, SQS1 to SQS6, with systematic variation of alkyl groups at the sp³-C and N-atoms of the indoline unit that is away from the anchoring group to control the dye-dye interactions on the TiO₂ surface. The branched alkyl groups help in modulating the self-assembly of sensitizers on the TiO₂ surface, besides passivating the surface that helps avoid the charge recombination processes. Light harvesting efficiency and cyclic voltammetry studies of dye-sensitized TiO₂ electrodes indicate that the aggregation and charge hopping process between the dye molecules can be modulated, respectively, by systematically increasing the number of carbon atoms in the alkyl groups. Such a variation in the branched alkyl group helps enhance V_oc from 672 (SQS1) to 718 mV (SQS6) and J_sc from 7.95 (SQS1) to 12.22 mA/cm² (SQS6), with the device efficiency ranging from 3.82% to 6.23% without any coadsorbent. Dye SQS4 achieves the highest efficiency of 7.1% (V_oc = 715 mV, J_sc = 13.05 mA/cm²) with coadsorbent chenodeoxycholic acid (CDCA) using an iodine (I^-/I₃^-) electrolyte compared to its analogues. An analysis of the incident photon-to-current efficiency profiles indicates that the major contribution to photocurrent generation is from the aggregated squaraine dyes on TiO₂.

Photophysical properties of porphyrinic covalent cages endowed with different flexible linkers

In-depth photophysical studies of four flexible covalent cages bearing either two free-base porphyrins or one free-base porphyrin and one Zn(II) porphyrin, connected by linkers of different lengths, are reported. In the case of the cages with two free-base porphyrins, exciton coupling between the porphyrins is evidenced by large and split Soret bands in the absorption spectra, but the different length of the linkers has only a slight effect on their emission properties. Strong electronic interactions between the porphyrins are also evidenced for the cages that incorporate a free-base porphyrin and a Zn(II) porphyrin, with a more pronounced splitting of the Soret band for the system with longer linkers. In these cages, following excitation of the Zn-porphyrin component, an almost quantitative energy transfer to the free-base unit occurs, with a rate 1.4 times faster in the cage with longer linkers (1.4 × 10[Formula: see text] s[Formula: see text] vs. 1.0 × 10[Formula: see text] s[Formula: see text]. This difference might reflect the more flattened conformation adopted by the cage equipped with longer and more flexible linkers, the latter allowing for a shorter interplanar distance between the porphyrins. The results are discussed in terms of classical and short-range energy transfer mechanisms.

Efficient Sunlight Harvesting by A4 β-Pyrrolic Substituted ZnII Porphyrins: A Mini-Review

Dye-Sensitized Solar Cells (DSSCs) are a highly promising alternative to conventional photovoltaic silicon-based devices, due to the potential low cost and the interesting conversion efficiencies. A key-role is played by the dye, and porphyrin sensitizers have drawn great interest because of their excellent light harvesting properties mimicking photosynthesis. Indeed, porphyrins are characterized by strong electronic absorption bands in the visible region up to the near infrared and by long-lived π^* singlet excited states. Moreover, the presence of four meso and eight β-pyrrolic positions allows a fine tuning of their photoelectrochemical properties through structural modification. Trans-A₂BC push-pull Zn^II porphyrins, characterized by a strong and directional electron excitation process along the push-pull system, have been extensively investigated. On the other hand, A₄ β-pyrrolic substituted tetraaryl Zn^II porphyrins, which incorporate a tetraaryl porphyrinic core as a starting material, have received lower attention, even if they are synthetically more attractive and show several advantages such as a more sterically hindered architecture and enhanced solubility in most common organic solvents. The present contribution intends to review the most prominent A₄ β-substituted Zn^II porphyrins reported in the literature so far for application in DSSCs, focusing on the strategies employed to enhance the light harvesting capability of the dye and on a comparison with meso-substituted analogs.

Electrochemical, Spectroelectrochemical, and Structural Studies of Mono- and Diphosphorylated Zinc Porphyrins and Their Self-Assemblies

Three series of porphyrins containing a Zn(II) central metal ion and zero, one, or two phosphoryl groups at the meso-positions of the macrocycle were characterized as to their electrochemical, spectroscopic, and structural properties in nonaqueous media. The investigated compounds are represented as 5,15-bis(4'-R-phenyl)porphyrinatozinc, 10-(diethoxyphosphoryl)-5,15-bis(4'-R-phenyl)porphyrinatozinc, and 5,15-bis(diethoxyphosphoryl)-10,20-bis(4'-R-phenyl)porphyrinatozinc, where R = OMe, Me, H, or CN. Linear-free energy relationships are observed between the measured redox potentials at room temperature and the electronic nature of the substituents at the 5 and 15 meso-phenyl groups of the macrocycle. The mono- and bis-phosphoryl derivatives with two p-cyanophenyl substituents provide electrochemical evidence for aggregation at low temperature, a greater degree of aggregation being observed in the case of 5,15-bis(diethoxyphosphoryl)-10,20-bis(4'-cyanophenyl)porphyrinatozinc(II). This compound was characterized in further detail by variable-temperature ¹H and ³¹P{¹H} NMR spectroscopy in solution combined with single crystal X-ray analysis in the solid state. The data obtained from these measurements indicate that this porphyrin has a dimeric structure in CDCl₃ at 223-323 K but forms a 2D polymeric network when it is crystallized from a CHCl₃/MeOH mixture.

Axial coordination reactions with nitrogenous bases and determination of equilibrium constants for zinc tetraarylporphyrins containing four β,β′-fused butano and benzo groups in nonaqueous media

The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH2Cl2 for derivatives containing four [Formula: see text],[Formula: see text]-fused butano or benzo groups and the equilibrium constants (log[Formula: see text] determined using spectral titration methods. The examined compounds are represented as butano(YPh)4PorZn and benzo(YPh)4PorZn, where Por is the porphyrin dianion and Y is a CH3, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano- and benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH2Cl2 and this leads to a 4–22 nm red-shift of the Soret and Q bands. The log[Formula: see text] values range from 1.98 to 4.69 for butano(YPh)4PorZn and from 3.42 to 5.36 for benzo(YPh)4PorZn, with the exact value depending upon the meso and [Formula: see text]-substituents of the porphyrin and the conjugate acid dissociation constants (p[Formula: see text] of the nitrogenous base.

Hybrid organic–inorganic supramolecular systems based on a pyridine end-decorated molybdenum(ii) halide cluster and zinc(ii) porphyrinate

Herein, first examples of supramolecular coordination bonded hybrids of Mo(ii) cluster and zinc(ii) porphyrinates are reported.

Electrochemistry of zinc tetraarylporphyrins containing fused butano and benzo groups. Effect of solvent and substituents on spectra, potentials and mechanism in nonaqueous media

Two series of zinc tetraarylporphyrins containing four [Formula: see text],[Formula: see text]′-pyrrole fused butano or benzo groups were synthesized and characterized as to their electrochemical and spectroelectrochemical properties in nonaqueous media. The examined compounds are represented as butano(Ar)4PorZn and benzo(Ar)4PorZn, where Por is the porphyrin dianion and Ar is a [Formula: see text]-CH3Ph, Ph or [Formula: see text]-ClPh substitutent on [Formula: see text]-positions of the macrocycle. Each Zn(II) butano- and benzoporphyrin undergoes two one-electron reductions to give a [Formula: see text]-anion radical and dianion in CH2Cl2. In contrast, three reductions were observed for the benzoporphyrin derivatives in pyridine, the third of which is assigned as electron addition to a benzophlorin anion generated from the doubly reduced benzoporphyrin. Two overlapped one-electron oxidations were observed for the butanoporphyrins in CH2Cl2, a result not previously observed for any other zinc porphyrin. The electrochemically measured HOMO-LUMO gap of the benzoporphyrins ranges from 1.89 to 1.90 V in CH2Cl2 and from 1.93 to 1.95 V in pyridine. Both values are smaller than the gaps of butanoporphyrins at 2.11-2.13 V in CH2Cl2 and 2.07.2.09 V in pyridine.

Push-Pull Zinc Porphyrins as Light-Harvesters for Efficient Dye-Sensitized Solar Cells

Dye-sensitized solar cell (DSSC) has been attractive to scientific community due to its eco-friendliness, ease of fabrication, and vivid colorful property etc. Among various kinds of sensitizers, such as metal-free organic molecules, metal-complex, natural dyes etc., porphyrin is one of the most promising sensitizers for DSSC. The first application of porphyrin for sensitization of nanocrystaline TiO2 can be traced back to 1993 by using [tetrakis(4-carboxyphenyl) porphyrinato] zinc(II) with an overall conversion efficiency of 2.6%. After 10 years efforts, Officer and Grätzel improved this value to 7.1%. Later in 2009, by constructing porphyrin sensitizer with an arylamine as donor and a benzoic acid as acceptor, Diau and Yeh demonstrated that this donor-acceptor framwork porphyrins could attain remarkable photovoltaic performance. Now the highest efficiencies of DSSC are dominated by donor-acceptor porphyrins, reaching remarkable values around 13.0% with cobalt-based electrolytes. This achievement is largely contributed by the structural development of donor and acceptor groups within push-pull framwork. In this review, we summarized and discussed the developement of donor-acceptor porphyrin sensitizers and their applications in DSSC. A dicussion of the correlation between molecular structure and the spectral and photovoltaic properties is the major target of this review. Deeply dicussion of the substitution group, especially on porphyrin's meso-position were presented. Furthermore, the limitations of DSSC for commercialization, such as the long-term stability, sophisticated synthesis procedures for high efficiency dye etc., have also been discussed.

Effect of the second chromophore energy gap on photo-induced electron injection in di-chromophoric porphyrin-sensitized solar cells

This work investigates the effect of the second chromophore energy gap on charge generation in porphyrin-based di-chromophoric dye-sensitized solar cells (DSSCs). Three di-chromophoric porphyrin dyes (PorY, PorO and PorR) containing three organic chromophores with decreasing frontier orbital energy offsets, including a carbazole-triphenylamine chromophore (yellow, Y), a carbazole fused-thiophene chromophore (orange, O) or a carbazole-thiophene benzothiadiazole thiophene chromophore (red, R), were investigated using optical and electrochemical methods, steady-state photoluminescence and photovoltaic device characterization. Energy transfer from the organic chromophore to the porphyrin was suggested in PorY and PorO as the main charge generation mechanism in DSSCs using these di-chromophoric dyes. On the other hand, electron transfer from the photo-excited porphyrin to the organic chromophore as a competing pathway leading to the loss of photocurrent is suggested for PorR-sensitized solar cells. The latter pathway leading to a loss of photocurrent is due to the lower lying lowest unoccupied molecular orbital of the additional organic chromophore (R) and suggests the limitation of the current di-chromophoric approach to increase the overall efficiency of DSSCs.

Porphyrin-sensitized solar cells: systematic molecular optimization, coadsorption and cosensitization

As a promising low-cost solar energy conversion technique, dye-sensitized solar cells have undergone spectacular development since 1991. For practical applications, improvement of power conversion efficiency has always been one of the major research topics. Porphyrins are outstanding sensitizers endowed with strong sunlight harvesting ability in the visible region and multiple reaction sites available for functionalization. However, judicious molecular design in consideration of light-harvest, energy levels, operational dynamics, adsorption geometry and suppression of back reactions is specifically required for achieving excellent photovoltaic performance. This feature article highlights some of the recently developed porphyrin sensitizers, especially focusing on the systematic dye structure optimization approach in combination with coadsorption and cosensitization methods in pursuing higher efficiencies. Herein, we expect to provide more insights into the structure-performance correlation and molecular engineering strategies in a stepwise manner.

Zn-Porphyrin propped with hydantoin anchor: synthesis, photophysics and electron injection/recombination dynamics

In this work, Zn-porphyrin with a hydantoin anchor (ZnPHy) was designed and synthesized for dye-sensitized solar cell (DSC) applications. The synthesized ZnPHy was well characterized using IR, NMR and mass spectral techniques, and satisfactory results were obtained. Cyclic voltammetry, UV-visible absorption, steady-state fluorescence, time-resolved fluorescence and transient absorption spectroscopic techniques were employed to elucidate the electrochemical and photophysical properties of ZnPHy. The obtained properties revealed that the synthesized ZnPHy can be used as a photosensitizer for DSC applications. The nature of ZnPHy binding onto the TiO₂ surface was investigated using ATR-FTIR and UV-Vis absorption measurements. The amount of adsorbed ZnPHy on TiO₂ surface was reasonably fit using the Langmuir adsorption isotherm, with a binding constant value of 1.03 × 10⁵ M^-1. Time-resolved measurements were used to elucidate the rate of electron injection and the regeneration and recombination kinetics for ZnPHy/TiO₂ film. The ZnPHy showed a high electron injection rate with a ϕ_inj of 99%. Intriguingly, the rate of electron recombination is much slower than the rates reported for carboxyl-based Zn-porphyrins. Such a high electron injection and slow electron recombination rate are beneficial to produce long-lived electrical current in a photovoltaic device. Thus, the ZnPHy-sensitized TiO₂ electrode showed the best photovoltaic performance, with the short-circuit photocurrent density (J_SC), open-circuit voltage (V_OC) and fill factor (ff) of 3.49 mA cm^-2, 0.6 V and 0.52, respectively, yielding an overall conversion efficiency (η) of 1.01%. For comparison, the ZnCOOH-sensitized electrode was also fabricated under the same conditions and yielded the η value of 0.84%. Hence, the hydantoin moiety could be a potential alternative anchoring group for DSC applications.

Ultrafast dynamics in co-sensitized photocatalysts under visible and NIR light irradiation

Activity modulation of co-sensitized light harvesting nanohybrids by tuning the ultrafast carrier dynamics under visible and NIR light irradiation.

Coupling of Zinc Porphyrin Dyes and Copper Electrolytes: A Springboard for Novel Sustainable Dye-Sensitized Solar Cells

The combination of β-substituted Zn²⁺ porphyrin dyes and copper-based electrolytes represents a sustainable route for economic and environmentally friendly dye-sensitized solar cells. Remarkably, a new copper electrolyte, [Cu(2-mesityl-1,10-phenanthroline)₂]^+/2+, exceeds the performance reached by Co^2+/3+ and I^-/I₃^- reference electrolytes.

Effect of fluorine substitution and position on phenylene spacer in carbazole based organic sensitizers for dye sensitized solar cells

The preparation of a series of organic dyes having a carbazole donor, cyanoacrylic acid as an acceptor, and phenylene ring as a spacer with the difference in the positions of fluorine substitution is reported. Due to its unique properties of small size and high electronegativity, fluorine is now being extensively used to control the optoelectronic properties of organic conjugated materials. In this study, the results revealed that the specific position and number of fluorine substitution were very crucial to control the optical as well as the electrochemical properties of organic dyes. It was found that fluorine substitution led to a redshift in the absorption spectra of the dyes and reduced the band gap. The injection rate of photoexcited electrons was measured using time-resolved photoluminescence and the o-fluoro substituted dye MA1F-o showed the best electron injection dynamics. As a result of broad absorption and high electron injection rate, the dye MA1F-o outperformed other dyes with a power conversion efficiency of 4.02% (J_sc = 8.3 mA cm^-2, V_oc = 0.75 V and FF = 0.64). The non-fluorinated dye MA0F exhibited a power conversion efficiency of 3.23% (J_sc = 6.8, V_oc = 0.72 and FF = 0.67). The dye MA1F-m exhibited the least molar absorption coefficient and a lower power conversion efficiency because of the meta inductive effect.

A long persistence phosphor tailored quasi-solid-state dye-sensitized solar cell that generates electricity in sunny and dark weathers

An all-weather quasi-solid-state dye-sensitized solar cell is built using a long persistence phosphor tailored mesoscopic TiO₂ photoanode and a three-dimensional conducting polymer gel electrolyte. The so-called all-weather solar cell yields a maximum efficiency of 28.7% in the dark, making a promising photovoltaic revolutionary for state-of-the-art photovoltaics.

One-pot synthesis of manganese porphyrin covalently functionalized graphene oxide for enhanced photocatalytic hydrogen evolution

In this paper, graphene oxide (GO) sheets covalently functionalized with (5,10,15,20-tetraphenyl) porphinato manganese(III) (MnTPP) has been successfully synthesized and tested as a photocatalyst for hydrogen evolution from water under UV-vis light irradiation. The obtained sample was systematically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis, Fourier transform infrared (FTIR), and Raman spectroscopy. The results show that the MnTPP moiety has been successfully grafted on the graphene oxide surface to form MnTPP modified GO (GO-MnTPP). The fluorescence quenching and photocurrent enhancement of GO-MnTPP confirm that the rapid electrons transfer from photoexcited the MnTPP moiety to the GO sheets. The platinized GO-MnTPP exhibits enhanced photocatalytic activity for water reduction to produce hydrogen. Moreover, with the assistance of polyvinyl pyrrolidone (PVP), the photocatalytic activity is further improved because of aggregation prevention of the GO-MnTPP nanocomposite. This study provides a facile method to build porphyrin-graphene-based photocatalysts for solar energy conversion.

Correlating excited state and charge carrier dynamics with photovoltaic parameters of perylene dye sensitized solar cells: influences of an alkylated carbazole ancillary electron-donor

Two perylene dyes characteristic of electron-donors phenanthrocarbazole (PC) and carbazyl functionalized PC are selected to study the complicated dynamics of excited states and charge carriers, which underlie the photovoltaic parameters of dye-sensitized solar cells (DSCs).

Core expanded, 21,23-dithiadiacenaphtho[1,2-c]porphyrin interactions with [60]fullerene

Saddle-shaped 21,23-dithiadiacenaphtho[1,2-c]porphyrin exhibits binding interaction with [60]fullerene in addition to photon absorption bands extending to 1000 nm.

A new ruthenium black dye design with improved optical properties for transparent dye sensitized solar devices

A new ligand for panchromatic Ru(ii) sensitizer yields 32% efficiency improvement over conventional “black dye” in transparent DSSCs.

Modifications of an unsymmetrical phthalocyanine: Towards stable blue dyes for dye-sensitized solar cells

A new copper phthalocyanine, namely 9(10),16(17),23(24)-tri-tert-butyl-2-[acetynyl-(4-carboxy)phenyl]phthalocyaninatocopper and its related free base have been synthesized as potential stable blue dyes for dye sensitized solar cells. The molecule structure consists on an unsymmetrically-substituted macrocycle bearing three tert-butyl groups and one phenylethynyl moiety as peripheral substituents and it is analogue to that of a previously published zinc derivative. Chemical and optical characterizations, as well as theoretical calculations of the frontier orbitals of both molecules are discussed. To evaluate the effect of the central metal on the photovoltaic behavior of this dye, the novel molecules have been both tested and confronted with the zinc derivative. This last one has shown efficiency values significantly higher than those previously published with a 2.10% maximum efficiency, while the other two dyes yielded 1.66% and 1.38% maximum efficiency respectively.