Dye Regeneration Research Articles

Optical and Photovoltaic Properties of New Synthesized Quinoxaline-2,3 Dione Derivatives for Efficient Dye Sensitized Solar Cell Application

In this study, the synthesis of 4 new heterocyclic compounds derived from quinoxalinedione were presented, which have been characterized by 1H and 13C NMR spectroscopy. The solar cells’ photovoltaic properties based on these novels organic compounds donor-π-acceptor dyes were studied. Density functional theory DFT method is realized to optimize electronic parameters, optical and photovoltaic properties for some new 8-hydroxyquinoline derivatives based on quinoxaline-2,3-dione. The results have shown that time-dependent DFT (TDDFT) investigations with polarizable continuum model PCM were significantly able to foretell the excitation energy and the spectroscopy of the molecule. The highest occupied molecular orbital HOMO and the lowest unoccupied molecular orbital LUMO energy levels of these molecules can ensure a positive impact on the dye regeneration and electron injection process. Injection driving force ΔGinject, light-harvesting efficiency LHE, reorganization energy λtotal and open-circuit photovoltage Voc provide qualitative predictions on these dyes’ reactivity. Among these 4 molecules, the compounds which can be used as organic solar cells have determined.
 HIGHLIGHTS
 
 We presented the synthesis and the characterization of a new series of heterocyclic compounds obtained by association of 8-hydroxyquinoline with quinoxalindione derivatives.
 The synthesis of this series of compounds was carried out by simple conditions but with good yields and the characterization data shows that there is good consistency between the spectroscopic data and the proposed structures
 These new compounds were obtained according to simple procedures with good yields and they have been the subject of a theoretical study
 This investigated process can be employed to predict the optical and photovoltaics properties on the other compounds and polymers, and it encourages to synthesis the novel organic solar cell materials
 
 GRAPHICAL ABSTRACT

A computational finding on the effect of π-conjugated acceptors in thiophene-linked coumarin dyes for potential suitability in DSSC application

Herein we studied the potential suitability of four thiophene-linked coumarin dyes in dye-sensitized solar cells (DSSCs) application by employing density functional theory (DFT) and time-dependent DFT methods. The new four dyes comprise various π-conjugated acceptor moieties, such as quinazolinone-N-acetic acid, indoline carboxylic acid, rhodanine acetic acid, and homophthalimide-N-acetic acid with dialkylamino coumarin as donor and thiophene as a common spacer. We have investigated the influence of the π-conjugated acceptor moieties in thiophene-linked coumarin dyes on the photovoltaic performance and adsorption onto the TiO2 surface. The π-conjugation in the acceptor moiety enhanced the intensity of the intramolecular charge transfer band and which has been corroborated by the natural bond orbital analysis. C3 dye showed higher charge separation (ΔqD–A) between the coumarin donor and rhodanine acetic acid acceptor moieties and which revealed a higher red-shift in the absorption spectra for C3 dye. The photophysical, electrochemical properties and photovoltaic parameters of DSSCs have been calculated to assess their suitability for the application in DSSCs. The higher dye regeneration driving force, higher lifetime, and higher power conversion efficiency values (calculated) make dye C3 the potential candidate for DSSCs among all the studied dyes.

Extraction, characterization and energy investigation of Garcinia kola, Cola Nitida and Cola Accuminata for efficient light absorption in dye-sensitized solar cells

Natural extracts were obtained from the Garcinia kola, Cola Nitida and Cola Accuminata. The extracts from Garcinia kola, Cola Nitida and Cola Accuminata were evaluated for their phytochemical, electrochemical and photovoltaic current–voltage (I-V) light-to-electricity conversion efficiency in dye-sensitized solar cells (DSSCs). This is the first time when flavonoid, garcinoic, caffeine and their derivatives from the Garcinia species will be tested for electrochemistry and for DSSCs power conversion efficiency. The results revealed that the different affinity among the three Garcinia sp.; Cola Nitida, Cola Accuminata and Garcinia kola with TiO2 semiconductor was responsible for their various adsorption, binding and light absorption transfer into the semiconductor band edge. Cyclic voltammetry of the three compounds shows a well-defined redox nature, good reversibility of electron transfer and dye regeneration. Cola Nitida NIT compound had the lowest Homo energy level (-5.130 eV) and highest Lumo energy value (-2.029 eV) than Garcinia kola and Cola Accuminata.GK compound revealed lower-charge transfer resistance than ACC and NIT. Gk sensitizer showed an improve light-to-electricity conversion efficiency (η2) = 0.14 %, FF = 0.753, Voc = 0.850 V and Jsc = 0.200 mAcm−2 under 1 sun illumination giving a standard deviation efficiency of 0.024 as compared to ACC and NIT.

Ruthenium (II) complexes bearing N‐heterocyclic carbene‐based C^N donor sets in dye‐sensitized solar cells

We present the syntheses of ruthenium (II) complexes bearing an N‐heterocyclic carbene (NHC)‐based C^N donor set and an NCS ligand and evaluate their use as photosensitizers in dye‐sensitized solar cells (DSSCs). These complexes deploy a monocarboxylic acid‐functionalized terpyridine (tpy)/phenyl‐tpy to anchor with the TiO2 of the photoanodes. Results show that the complexes devoid of the phenyl spacer between the acid anchor and the tpy harvest the visible light more effectively. Absorption of the visible light transfers the electron density from the ruthenium, NHC, and the NCS donors to the tpy acceptor (1MRuLdonorLacceptorCT). Stronger MRuLdonor σ‐bonds in the complexes with opposite NHC and tpy ligand configuration render facile ruthenium‐centered oxidation. In contrast, the metal‐centered oxidation of complexes with trans‐oriented NHC and NCS ligands is relatively difficult. However, these complexes display higher photon conversion efficiency (PCE) in DSSCs. One of them shows PCE of 3.44%, which is ~70% of the standard N3 dye, under similar conditions. A longer electron lifetime and the lowest charge transfer resistance at the TiO2/electrolyte interface derived from the electrochemical impedance spectra accounts for the enhanced PCE. Insights into the oxidized dye regeneration in a DSSC setup, obtained from the computed Hirshfeld charges and spin density, depict the essential role of iodide anion in dye regeneration. This report summarizes our investigation of photophysics, electronic structure calculations, and the electrochemical study of all newly prepared complexes and their use as photosensitizers in DSSCs.

Pyrrole – Best additional spacers for azo based dye sensitized solar cells: A computational study

Quantum chemical calculations have been performed in this article to study the effect of heterocyclic spacers on the azo based metal free Donor-π-Acceptor dyes. Six heterocyclic moieties were used as additional spacers in two different positions on a azo based dye to generate twelve different dye sensitizers and the progress on the optoelectronic properties and the efficiency of such dyes have been studied using density functional approach. According to our calculated properties like charge transfer analysis, light-harvesting efficiencies and driving forces like electron injections and dye regeneration for the free dye and dye-TiO2 complex, nitrogen based additional heterocyclic spacers (Pyrrole) showed to be the best additional spacer with high driving force leading to an increased efficiency for the dye sensitizer.

Ruthenium‐based complex dyes for dye‐sensitized solar cells

AbstractDye‐sensitized solar cell (DSC) has been a promising new‐generation photovoltaic technique. Sensitizer is one of the most important parameters that determine the photovoltaic performance of a DSC. This review article shows the step‐by‐step procedure of how to design high photovoltaic performance ruthenium‐based complex dyes for DSC. The strategy includes the extension of the conjugated length of the anchoring and ancillary ligands as well as using multidentated ligand and strong sigma donor to red‐shift to λmax of the metal‐to‐ligand charge transfer band and increase molar absorption coefficient, fine‐tune the functionality of the ligand to enhance dye regeneration, and using non‐mono‐dentated ligand to improve the dye stability. The review focuses on basic chemistry rather than the photovoltaic performance comparison between the ruthenium dyes introduced in this article.

Converting Solar Cells to Photocapacitors without the Incorporation of Additional Capacitive Components

Photocapacitors directly store the energy from light as electricity and are hence very cost-effective rechargeable power sources. High-performance photocapacitors most commonly consist of two devices, a solar cell that converts light to electricity and a capacitor that stores this electric energy. Such hybrid architecture is required since typical solar cells cannot efficiently retain the photogenerated charges in the dark and capacitors are not able to create charges through light. In this work, we demonstrate how dye-sensitized solar cells can be simply tuned to simultaneously act as a capacitor without having to introduce additional capacitive components. This is achieved by effectively suppressing the cell’s rapid charge recombination in the dark, thus minimizing self-discharging via excessive electron leakage within the device. The methods employed in attaining this feature involve the elimination of oxidizing species that could act as recombination centers in the electrolyte as well as the proper choice of the reducing agents with redox potentials yielding low dye regeneration rates. Hence, our solar cell photocapacitor allows simpler device fabrication and performance control as well as reduced material cost, in this way broadening its scope of utilization. Finally, a near-infrared solar cell photocapacitor is demonstrated as an example of a wirelessly and noninvasively chargeable power source for potential medical applications.

Effect of carboxylic acid and cyanoacrylic acid as anchoring groups on Coumarin 6 dye for dye-sensitized solar cells: DFT and TD-DFT study

Starting with Coumarin-6 dye, two novel D-π-A organic dyes C6X and C6N have been designed by attaching carboxylic acid and cyanoacrylic acid groups as anchoring groups to Coumarn-6 dye, respectively, to understand their potential use in dye-sensitized solar cells (DSSCs). The electronic structure and photophysical and photovoltaic properties of the novel designed dyes were studied using density functional theory DFT and time-dependent density functional theory TD-DFT with the Becke3-Parameter-Lee–Yang–Parr (B3LYP) functional and the 6-31G (d, p) basis set. Optimized structure and electronic properties (highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital (ELUMO), and energy difference (Eg) between HOMO and LUMO) were calculated showing that C6N has the smallest band gap with the larger absorption region. Density of states (DOS), molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis, non-linear optical (NLO) properties, UV–vis spectra, as well as some crucial parameters affecting the photovoltaic performance of DSSCs, such as light-harvesting efficiency (LHE), electron injection driving force (ΔGinject), dye regeneration driving force(ΔGreg), and the excited state life time(τe), were calculated to study the effect of the anchoring group on the DSSC performance. Additionally, the adsorption of C6X and C6N dyes on the TiO2 anatase (101) surface and the mechanism of electron injection were also investigated using a dye–(TiO2)9 cluster model using TD-B3LYP calculation. The calculated adsorption energies of the dyes suggest a strong adsorption of dyes to a TiO2 surface. The results show that C6N may be theoretically a good candidate as sensitizer of DSSC application.

Excited-state properties of newly sensitized imidazole-arylamine-based organic DSSC sensitizers in solvent and adsorbed on TiO2/FTO support

Six recently synthesized arylamine-imidazole combo dyes, utilized in dye-sensitized solar cells staining TiO2 semiconductor, were spectroscopically investigated. Studies were performed with application of steady-state and time-resolved absorption spectroscopies and were done on dyes dissolved in dichloromethane and anchored on TiO2/FTO film support. The investigations allowed to characterize the excited state decay dynamics of individual compounds, determine time constants of dye-to-TiO2 electron injection process for dyes adsorbed on TiO2/FTO support and subsequent recombination and dye regeneration dynamics. These studies were performed on bare dye/TiO2/FTO photoanodes in air environment and, if possible, on the same samples with dye layer immersed in electrolyte solution. These evaluations allowed to determine approximate time constants for dye regeneration and directed toward dye that reveals most advantageous properties and hypothetically should outperform its counterparts as TiO2 sensitizer.

Effect of an aqueous copper gel electrolyte with cobalt metal organic framework based additive on performance of aqueous-dye-sensitized solar cells

A simple mono-dentate ligand substitution approach was studied to design three new potential tunable heteroleptic copper redox mediators with general formula [Cu (bnbip) (X)]1+/2+ where, bnbip is a tridentate ligand, (2,6-bis(1-(naphthalen-2-ylmethyl)-1H-benzo[d]imidazol-2-yl)pyridine), X = 4-tert-butylpyridine (tbp), 4-chloropyridine (cp) and 5-methoxy-1-(pyridin-4-yl)-1H-indole (mpi). Herein, copper mediator bearing bulky high donor ligand (mpi) reached best redox potential of 0.72 V vs NHE, which directly improves Voc and Jsc of the dye-sensitized solar cells (DSSC) devices because of its lower reorganization energy and driving force. A series of six aqueous gel electrolytes were prepared as G-1, G-2, G-3 (without additive) and G-4, G-5, G-6 (with Co-MOF additive) to analyze the role of three different heteroleptic copper redox couples and Co-MOF in aqueous gelrite polymer electrolytes. Impressively, electrolytes G-4, G-5 and G-6 affords higher PCE of 2.03, 2.12 and 3.42% under 1sun condition than electrolytes without additives, which proves the role of Co-MOF as an additive to reduce recombination process. This control in recombination occurred due to high interaction of repeating carboxylate donor groups of additive with TiO2 surface and Cu2+ ion of redox pair. The electrolyte material G-6 consists of Cu+1/+2[(bnbip)(mpi)] redox mediator, Co-MOF additive and aqueous geltrite polymer host obtained higher Jsc and PCE which were sustained via many aspects, such as high conductivity, larger charge, higher chemical capacitance, longer electron lifetime, a shift in the quasi-Fermi level of TiO2, lower recombination of electrons and fast dye regeneration.

Improved Dye Regeneration through Addition of a Triphenylamine Electron Donor in Iodide-Based Electrolytes for Dye-Sensitized Solar Cells

The addition of a small organic electron donor, tris(p-anisyl)amine (TPAA), to an iodide/triiodide electrolyte for dye-sensitized solar cells was found to give pronounced effects on charge transfer reactions. When using the organic dye LEG4 as a sensitizer, an improved solar cell performance was found, which could be attributed to the extremely rapid dye regeneration reaction when TPAA is added. In contrast, for the ruthenium dye N719, no significant solar cell improvement was found, despite rapid dye regeneration. Using transient absorption measurements, it was found that reduction of the intermediate TPAA+ by iodide is sluggish. This allows for significant recombination of electrons in TiO2 to TPAA+ when the adsorbed dye layer does not have sufficient electron-blocking properties.

Influence of heteroatoms on the optoelectronic properties of triphenylamine-based dyes for DSSCs application: A computational approach

A series of sensitizers with D-π-π-A architectural framework have been fine-tuned through a variation of heteroatoms (NH, O, Se, and Te) in the π-spacers. Cyanoacrylic acid and hydantoin were used as the acceptor groups. The geometrical and electronic properties were investigated through density functional theory (DFT) and time-dependent DFT (TD-DFT) , respectively. To determine stable dye-TiO2 configuration, the binding energies are reported. The driving force of charge injection and dye regeneration range between 0.00 to −0.77 eV and −0.133 to −1.60 eV, respectively, suggesting spontaneous processes. Chalcogen heteroatoms (S, Se, and Te) improved absorption within the visible and NIR regions. The binding energies of dye on (TiO2)6 cluster range between −8.32 to −9.62 eV and −7.77 to −8.98 eV for cyanoacrylic acid and hydantoin dyes, respectively. The findings suggest that the inclusion Se and Te heteroatoms may boost the performance of DSSCs when compared to parent materials containing S.

D–π–A manufactured organic dye molecules with different spacers for highly efficient reliable DSSCs via computational analysis

ABSTRACT Based on (E)-2-cyano-3-(5-(2-(4-(dimethylamino)phenyl)ethynyl)thiophene-2-yl)acrylic acid (CSD-01) dye, newly designed isolated organic (CSDS1-CBDS7) molecules were investigated for dye-sensitised solar cells (DSSCs) application using the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The electronic and optimised geometry of the CSDS1–CSDS7 derivatives were contained in the electron-donor (D), π-linker (π) and electron–acceptor (A) groups to form a D–π–A structure. Different hybrid functionals were used to get a maximum value of optical absorption UV-Vis peak in CSD-01 dye. Accordingly, a ωB97XD was sensibly found by calculating the UV-Vis in CSD-01. Further, UV-Vis spectra were used to design newly efficient sensitisers by the TD-DFT-ωB97XD-6-31G(d) theory. The CSDS1–CSDS7 dyes were implemented on the driving force of the electron injection (), dye regeneration (), dipole moment (), light-harvesting efficiency, theoretical open-circuit photovoltage (), excited-state lifetime (τ), the density of state, the exciton binding energy () and molecular electrostatic potential. The highest occupied molecular orbitals below the redox electrolyte and lowest unoccupied molecular orbitals above the conduction band edge of the TiO2 surface were successfully identified. Finally, the newly CSDS5 and CSDS6 structured sensitisers were offered theoretical tools for highly efficient organic photosensitisers for further research.

Replacing naphthalene with anthracene π-bridge improves efficiency of D-π-A triphenylamine dyes-based dye-sensitized solar cells

Two novel D-π-A framework type of dyes involve to a N,N-diphenylaniline (DPA) as electron donor (D) and naphthalene/anthracene π-bridge mediated between diazo (NN) functional group and carboxyl acid as an anchoring unit were designed, synthesized and utilized for dye-sensitized solar cells (DSSCs) applications. The dye, DPA-azo-N, contains a naphthalene aromatic π-bridge mediated between carboxylic acid anchor and the DPA using diazo (NN) functional group, while the dye, DPA-azo-A, uses the anthracene π-bridge. The inclusion of one more aromatic ring in the π-bridge unit of dye molecules surprisingly changed the optical and electrochemical properties of dye from DPA-azo-N to DPA-azo-A, which attributed to the fine-tune ability of this synthetic strategy for engineering the levels of energy in the dyes. The DSSCs with DPA-azo-N as a sensitizer and a I3−/I− standard electrolyte resulted 4.60% for photovoltaic conversion efficiency (η) under the air mass (AM) 1.5 G standard irradiation condition, which gained η for DSSCs those that were involved DPA-azo-A greater η (5.01%) under same irradiation conditions. For the DPA-azo-N, and DPA-azo-A sensitizers, the influence of π-bridge structure on highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels were used for obtaining the energetically well-fit condition of the I3−/I− electrolyte redox potential and TiO2 conduction bond (CB) and also efficient dye regeneration. The results inferred that synthesizing a long conjugated π-bridge unit of sensitizers can increase the η in DSSCs.

An Ab Initio Molecular Dynamics Study of the Mechanism and Rate of Dye Regeneration by Iodide Ions in Dye-Sensitized Solar Cells

In the ambition to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs), it will be essential to understand the mechanisms and rates of dye regeneration. Although the mechanism of dye regeneration has been studied by static density functional theory (DFT) and classical molecular dynamics (CMD) simulations, ab initio molecular dynamics simulation (aiMD) has the potential to combine the insights from both methods for a deeper understanding. In this work, a series of aiMD simulations has been performed to study the interaction between an oxidized organic model dye, LEG4, and an electrolyte containing iodide ions as reducing agents. Dynamic Mulliken and natural spin population analyses show that two iodide ions, I–···I–, are required for dye regeneration. It was found that a distance between I–···I– of less than 6.5 Å at site 1 benefits from the electrostatic environment of the triphenylamine group of the LEG4 dye, and a corresponding distance of 4.8 Å at site 2 is essential for the dye regeneration process to take place. The rate constants of the LEG4 regeneration by two iodine ions range from 105 to 1012 s–1, spanning a window in which results from both experimental and static theoretical calculations fall. It is also verified that the probability of electron transfer from a radical I2– to the oxidized LEG4 dye is extremely low due to the rapid electron back-transfer. However, it has been found that the addition of an additional iodide ion at a distance of 5 Å with respect to the radical I2– opens the pathway for the reduction of the oxidized LEG4 dye with an associated formation of I3–. The current results highlight the necessity for a dynamical approach for a full understanding of the regeneration process.

Investigation on Dye Regeneration Kinetics at P‐Type Sensitized Nanoparticle Nickel Oxide Film by Scanning Electrochemical Microscopy

The efficiency of a NiO‐sensitized solar cell is determined by the kinetics of hole injection and dye regeneration reactions at the NiO/dye/electrolyte interface. In this research, the photochemical regeneration kinetics of dye adsorbed on the NiO film was investigated by scanning electrochemical microscopy (SECM). Besides, organic C343 and P1 sensitizers in combination with iodide‐based, cobalt‐based, and thiolate‐based electrolytes were selected to understand the effect of sensitizers and redox shuttles on the dye regeneration process. As a result, a fast regeneration kinetic rate constant was conformed in the thiolate‐based sample compared with cobalt‐based and iodide‐based, demonstrating that the organic redox shuttle was an efficient mediator to optimize the performance of p‐type DSSC. Furthermore, the regeneration rate constants (keff), reduction rate constants (kred), and absorption cross section (Фhv) were investigated for organic dyes and electrolytes. That is, an effective dye regeneration rate constant kred of 6.95 × 105 mol-1cm3s-1 for NiO/P1 and kred of 3.75 × 105 mol-1cm3s-1 for NiO/C343 was found at various wavelengths. Therefore, the experimental results demonstrate that regeneration kinetics are dependent on the type of electrolyte and dye used. Moreover, the results suggest that scanning electrochemical microscopy is a powerful method for screening efficient dyes and electrolytes for charge transfer reactions in P‐type dye‐sensitized solar cells.

Dye Regeneration Kinetics of C343-Sensitized Nickel Oxide Investigated by Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) feedback mode has been used to investigate kinetics of dye regeneration in DSSC. Organic dye C343 and CW1 are used as sensitizers for nickel oxide (NiO) photoelectrochemical cells. The influence of film thickness on dye regeneration kinetics in the films for NiO/C343 for six different films was investigated. SECM was used to analyze effective rate constant, keff and reduction rate kred, absorption cross section, Φhv for the dye regeneration process. The data reveal a significant variation of keff and kred with a variation of light intensity, sample thickness and dye difference. This research found remarkable dependence of the dye regeneration kinetic parameters on illumination flux, dye types and film thickness of electrode.

Design of two novel dyes having maximum absorption in infrared region: A DFT investigation

The first dye sensitized solar cell (DSSC) was designed by O'regan and Grätzel in 1991 using ruthenium-based metal complex. Over the years, scientists have thoroughly investigated DSSCs, achieving efficiencies greater than 10%. Present investigation focusses on two novel dyes based on D-π-A and D-π-A-A models for application in DSSC. Absorption region of the sensitizers is expected to lie in the infrared region. Both dyes have same donor and π-bridge moieties, which are carbazole and thiophene respectively. In the first dye (DYE 1), naphthalimide is acceptor, whereas, in the second dye (DYE 2), naphthalimide and benzothiadiazole act as acceptors. The dye structures have been optimized under the framework of density functional theory (DFT) at B3LYP/cc-pVDZ theory level using Gaussian 16W software package. TDDFT calculations were performed at CAM-B3LYP/cc-pVDZ theory level to check absorption maxima in both dyes. TDDFT results confirm that both dyes have absorption profile in the infrared region. DYE 1 and DYE 2 have maximum absorption wavelengths at 1432 nm and 1351 nm respectively. Other parameters calculated for the dyes are light harvesting efficiency, charge injection energy, dye regeneration energy and open circuit voltage.

Impact of internal (donor/acceptor) moieties and π-spacer in triphenylamine-based dyes for DSSCs

The impact of internal (donor/acceptor) groups and π-spacers (benzene/thiophene) are investigated in dye-sensitized solar cells (DSSCs) using a series of D-A-π-A and D-D-π-A type organic dyes. These dyes have a triphenylamine donor, different internal acceptor (A) or donor (D) groups and thiophene/benzene as a π-spacer combined with an acceptor cyanoacrylic acid. Density functional theory (DFT) and time-dependent DFT (TDDFT) approaches were used to investigate the dye geometries, as well as electronic excitations and charge transport characteristics. The frontier molecular orbital energies and energy gaps facilitated for the consideration of appropriate energy levels for dye regeneration, electron transfer and electron injection. The short circuit current density (JSC) calculations were achieved by using dye regeneration energy (ΔGreg), injection driving force (ΔGinj) and light harvesting efficiency (LHE). Charge transport properties like electron affinities (EA), ionization potentials (IP), along with reorganization energies (λh and λe) are also described. The outcomes show that adding an internal donor/acceptor in D-π-A arrangement and different π-bridge influences the absorption energies and enhanced photovoltaic characteristics. As a result, the fundamental goal of this research is to establish a theoretical foundation for appropriate structural changes and design in the development of efficient DSSCs.

Inhibited interlayer electron transfer in metal ion linked multilayers on mesoporous metal oxide films

The incorporation of dye-electron donor motifs on metal oxide surfaces is a common strategy to increase dye regeneration rate, slow recombination, and improve overall dye-sensitized device performance. Here we used zinc ion linked multilayer assembly of a dye (N3) and a cobalt polypyridyl electron donor (Co) on TiO2 as an alternative to traditional covalently linked dye-donor systems. The formation of the TiO2-N3-Zn-Co multilayer was monitored using UV–Vis and ATR-IR and we introduced inductively coupled plasma mass spectrometry as a means of quantifying the surface loading of spectroscopically obscured molecules like Co. Interestingly, and contrary to the original intent, the addition of Co electron donor impeded the dye-sensitized device in nearly every performance metric. Transient absorption measurements indicate that both excited state quenching of N3 by Co and Co to N3+ electron transfer are slower than the intrinsic excited state decay and recombination, respectively. We suggest that the geometric restriction imposed by the metal ion linked architecture sufficiently slows electron transfer such that Co is effectively inert in this assembly. While this bilayer did not improve device performance, these insights may guide new design strategies that will improve performance and/or will be of use in other applications where electron transfer is not desired but say communication of spin and/or magnetic moment is needed.