Donor Antenna Research Articles

D–π–A organic dyes derived from the indacenodithiophene core moiety for efficient dye-sensitized solar cells

Indacenodithiophene-core-based D–π–A-type organic sensitizers with two different donor antennas (triphenylamine and phenothiazine) were designed and synthesized for use as light-harvesting materials in dye-sensitized solar cell (DSSC) applications.

Cover Feature: BOPHY‐Fullerene C60 Dyad as a Photosensitizer for Antimicrobial Photodynamic Therapy (Chem. Eur. J. 5/2022)

A heavy-atom-free BOPHY-based photosensitizer (PS) has been obtained as a mixture of two atropisomers. The BOPHY core works as a visible light-harvesting center and donor antenna, while a fullerene C60 acceptor acts as an effective spin converter and triggers photodynamic action. The dyad is capable of producing reactive oxygen species (ROS) by both photodynamic mechanisms. In-vitro studies indicate that the dyad photokills microorganisms after visible light irradiation. More information can be found in the Research Article by D. A. Heredia et al. (DOI: 10.1002/chem.202103884).

The molecular engineering, synthesis and photovoltaic studies of a novel highly efficient Ru(ii) complex incorporating a bulky TPA ancillary ligand for DSSCs: donor versus π-spacer effects.

A novel Ru(ii) complex, denoted as IA-7, incorporating a bulky donor antenna, was synthesized and characterized as a promising inexpensive alternative to conventional p–n junction solar cells to study the influence of a bulky donor antenna on the light harvesting efficiency (LHE), ground and excited state oxidation potentials and total conversion efficiency of sunlight to electricity (% η) for dye-sensitized solar cells (DSSCs), and the device performance was compared to devices with MH-12 and MH-13 dyes. The incorporation of the bulky donor enriched triphenylamine (TPA) antenna resulted in a considerable increase in JSC and η values for DSSCs, where IA-7 outperformed MH-12 and MH-13 in terms of the total conversion efficiency and achieved a power conversion efficiency (η) of 8.86% under full sunlight irradiation (100 mW cm−2), compared to 8.09% for MH-12 and 8.53% for MH-13, which can be ascribed to the high open circuit voltage (VOC) of IA-7. Molecular engineering utilizing DFT/TD-DFT was employed to calculate the electronic properties of IA-7, including the HOMO/LUMO isosurfaces, the lowest singlet–singlet electronic transitions (E0–0), and the ground and excited state oxidation potentials, which were in ideal agreement with the empirical results. The electronic distribution of IA-7 indicated that the HOMO is delocalized not only on Ru and NCS, but also on the substituted TPA, and the LUMO is delocalized over 4,4′-bipyridyl dicarboxylic acid.

In-Silico Design of a Donor–Antenna–Acceptor Supramolecular Complex for Photoinduced Charge Separation

We investigate via density functional theory a series of donor–antenna–acceptor molecular rectifiers designed as modules for artificial photosynthesis devices. We consider triad modules containing phenothiazine (PTZ) as the electron donor and different derivatives of naphthalene diimide (NDI) as the antenna and secondary electron acceptor. The choice of the molecular components in the triad is guided by the redox and optical properties of each subunit. Using time-dependent DFT in combination with the long-range corrected xc-functional CAM-B3LYP we investigate how photoinduced charge transfer states are affected by systematic modifications of the triad molecular structure. In particular, we show how by controlling the length of the molecular bridges connecting the different charge separator subunits it is possible to control the driving force for the relaxation of the excitonic state into the full charge-separated state. On the basis of these findings we propose a supramolecular triad consisting of inexpensive and readily available molecular components that can find its implementation in artificial devices for solar energy transduction.

Highly efficient light-harvesting boradiazaindacene sensitizers for dye-sensitized solar cells featuring phenothiazine donor antenna

A series of novel 2,6-disubstituted boradiazaindacene (BODIPY) metal-free organic dyes (UY1–4) with phenothiazine (PTZ) moiety as electron donor for the dye-sensitized solar cells (DSSCs) have been designed and synthesized. Their photophysical, electrochemical and photovoltaic properties are extensively investigated. The structure–property relationship shows that the introduction of double donor–acceptor (D–A) branch and BODIPY-thiophene as the π-conjugated bridge is favorable to improve the efficiency of DSSCs. Among these dyes, UY4 comprised of double D–A branch with PTZ units as electron donor, a BODIPY-thiophene unit as bridge and 2-cyanoacrylic acid unit as electron acceptor possesses a stronger donating ability and longer absorption band. Hence, a DSSCs using UY4 showing best photovoltaic performance with a short-circuit photocurrent density (Jsc) of 12.16 mA cm−2, an open-circuit photovoltage (Voc) of 0.59 V and a fill factor (ff) of 0.68, corresponding to an overall conversion efficiency (η) of 4.89% under AM 1.5 irradiation (100 mW cm−2). This is the best reported result in the solar cell with a BODIPY dye as photosensitizer.

Invited Presentation: 1PA- and 2PA-PDT Photo-Inactivation of Cancer Cells with Deca- or Icosacationic [70]Fullerenes with Light Absorbing e‒-Donor Antenna

We report the synthesis and anticancer photodynamic properties of two new decacationic fullerene (LC14) and red light-harvesting antenna-fullerene conjugated monoadduct (LC15) derivatives. The antenna of LC15 was attached covalently to C60> in a close distance to cage of only <3.0 Ǻ to facilitate ultrafast photoinduced intramolecular electron-transfer (for type-I photochemistry) and photon absorption at long wavelengths up to 600 nm. Because LC15 was more hydrophobic than LC14 we compared formulation in Cremophor EL micelles with direct dilution from dimethylacetamide (DMA). We excited the fullerenes either with UVA (340‒380 nm) or white (400‒700 nm) light and studied their ability to generate singlet oxygen (1O2) and hydroxyl radicals (HO·) using specific fluorescent probes. HeLa human cervical cancer cells were studied in vitro for loss of viability, apoptosis and location of subcellular damage. LC14 produced more 1O2 than LC15, while LC15 produced much more HO· than LC14. When delivered by DMA, LC14 killed more HeLa cells than LC15 when excited by UVA light, while LC15 killed more cells than LC14 when excited by white light consistent with the antenna effect. However LC15 was more effective than LC14 when delivered by micelles regardless of the excitation light. Apoptosis was produced more rapidly after illumination by micellar fullerenes compared to DMA delivery. Intracellular damage was more pronounced after micellar delivery and affected the endoplasmic reticulum as well as lysosomes and mitochondria. These novel structures may be used as photostable photosensitizers for topical application to superficial cancer.

Highly efficient light harvesting ruthenium sensitizers for dye-sensitized solar cells featuring triphenylamine donor antennas

Ruthenium complexes featuring triphenylamine donor antennas boost dye-sensitized solar cell devices' power conversion efficiency close to 11%.

Molecular nanocluster fluorescence in microwave infrared-radiation fields

The paper considers a donor-acceptor nanocluster fluorescing in a microwave infrared radiation field. It is assumed that the nanocluster consists of two dipole-dipole interacting organic molecules. It is shown that the fluorescence process of the nanocluster occurs if the donor molecule contains a substructure of identical diatomic pairwise interacting bonds of dipoles (an IR antenna). This antenna is capable of accumulating vibrational energy as a sum of collective vibrational quanta (excimols). The acceptor molecule has no permanent dipole moment and cannot be excited by microwave IR radiation. This molecule is polarized in the dipole moment field of the donor IR antenna and can receive energy accumulated in the IR antenna of the donor molecule. If the acceptor molecule has an electronically excited state in the long-wavelength visible region of its absorption spectrum, then after receiving energy equal to the energy of this state from the donor antenna, the electronic excitation of the acceptor molecule and its fluorescence is possible. As an example, the fluorescence of a nanocluster is considered whose donor molecule has a C n H2n IR antenna. The acceptor molecule is aromatic and the external infrared frequency, 1.1 × 1014 s−1, is equal to the frequency of the excimol in the donor infrared antenna.

Theoretical Study of New Heteroleptic Ruthenium Complex with Conjugated Phenoxazines

In this study, novel ruthenium complexes substituted with donor antenna group were designed and studied theoretically to enhance the photovoltaic. We have compared the well known N3 dye and Ru(II) complexes substituted with antenna groups, such as a conjugated phenoxazine (POZ) of one site, two conjugated POZs of both site to bipyridine. Molecular orbital analysis confirmed that the HOMOs of N3 are localized over the NCS ligand orbitals of N3, however, the HOMO, HOMO-1 and HOMO-2 of Ru(dcbpy)(pbpy)(NCS)2 and Ru(dcbpy)(dpbpy)(NCS)2 are localized over the NCS or POZ antenna ligand. The TDDFT calculations showed that the complexes with POZ donor antenna had panchromatic absorption spectra in the region above 400 nm compared to N3 dye. Absorption bands between 400 and 500 nm were ascribed to transitions of antenna unit. From these results, it is shown that substituted antenna moiety enhanced their electronic and optical properties as dye sensitizer, and it is expected that these ruthenium complexes with POZ antenna would show better performance than N3 dye in conversion efficiency for DSSCs.

A Study on Improved Isolation of Indoor Repeating Antenna using Metamaterial Absorber for WCDMA System

This paper proposes a novel design for a compact, high-isolation WCDMA indoor repeater antenna. The proposed antenna consists of a patch antenna and metamaterial absorber. The required WCDMA bandwidth is obtained by utilizing the coupling between the main and the parasitic patches. In addition, high isolation is achieved using the metamaterial absorber, which has an absorption of about 98% at 2.1 GHz. Overall, the proposed antenna has a gain of over 7 dBi, a Voltage Standing Wave Ratio (VSWR) of less than 2, more than 85 dB of isolation between the service and donor antennas over the WCDMA band and a total volume of the proposed antenna only 70 mm × 70 mm × 43.8 mm.

Interference Cancellation Algorithm for 2&amp;amp;#215;2 MIMO System without Pilot in LTE

Interference cancellation system (ICS) for 3GPP/LTE system is the broadband cancellation system, which receives forward signal through the donor antenna. We proposed new algorithm of received signal with pilot and non-pilot design. Although repeater design needs our project, so in this paper we discuss about interference cancellation algorithm for 2x2 MIMO systems without pilot in LTE. First explain the general principle structure of 3GPP/LTE, next determine our new design and algorithm. Finally, we simulated our mathematic extraction of proposed new algorithm on MATLAB.

Isolation Improvement of a Microstrip Patch Array Antenna for WCDMA Indoor Repeater Applications

This paper presents the isolation improvement techniques of a microstrip patch array antenna for the indoor wideband code division multiple access (WCDMA) repeater applications. One approach is to construct the single-feed switchable feed network structure with an MS/NRI coupled-line coupler in order to reduce the mutual coupling level between antennas. Another approach is to insert the soft surface unit cells near the edges of the microstrip patch elements in order to reduce backward radiation waves. In order to further improve the isolation level, the server antenna and donor antenna are installedinorthogonal direction. The fabricated antenna exhibits a gain over 7 dBi and higher isolation level between server and donor antennas below −70 dB at WCDMA band.

Isolation Enhancement between Indoor Repeater Antennas with Chip Resistor Embedded FSS

The isolation enhancement between the donor antenna and the service antenna for indoor repeater systems is presented by using a frequency-selective surface (FSS). A unit cell of the proposed FSS consists of a quarter-wavelength resonator, a chip resistor, an FR4 substrate, and a ground plane. Applying the unit cells of the proposed FSS embedded a chip resistor on the side walls of each reflector for indoor WCDMA repeater antennas and aligning them along with the cross-polarization of each antenna, the isolation is improved by about 13 dB at the WCDMA band.

Thickness dependence of device parameters in solid state dye sensitized solar cells

A solid-state dye-sensitized solar cell (SDSC) was fabricated with a very thin (~ 650 nm) mesoporous TiO2 electrode and a donor-antenna (D-A) dye by using 2,2',7,7'- tetrakis - (N,N-di-p-methoxyphenyl-amine) 9,9'- spirobifluorene (Spiro OMeTAD) as hole conductor. A highly transparent thin electrode sensitized with D-A dye showed a short circuit current (Isc) of 4.10mA/cm2, an open circuit voltage (Voc) of 782 mV and an efficiency of 1.79 % at an illumination intensity of 100 mW/cm2 (1 sun, AM 1.5G). TiCl4 treatment of mesoporous TiO2 layer resulted in Isc of 6.18 mA/cm2, Voc of 737 mV and an efficiency of 2.12% at the same illumination intensity. This investigation demonstrates the possibility of fabrication of SDSC by way of using a very thin and transparent TiO2 electrode together with a high molar extinction coefficient D-A dye, and the effect of TiO2 layer thickness on solid-state solar cell performances is discussed. Keywords: Donor - antenna dye, sensitization, solid-state dyesensitized solar cell, TiO2, transparent electrode. Doi: 10.4038/jnsfsr.v39i1.2921 J.Natn.Sci.Foundation Sri Lanka 2011 39 (1): 35-42

Integration of TiO2nanotube arrays into solid-state dye-sensitized solar cells

In this investigation, transparent TiO 2 nanotube arrays prepared on a FTO substrate are employed as 1D nanostructures providing elongated direct pathways for electron transport and collection in solid-state dye-sensitized solar cell (SDSC). Donor-antenna (D-A) dyes provide an exciting route for improving the light harvesting efficiency in dye sensitized solar cells owing to their high molar extinction coefficients and the effective spatial separation of charges in the charge-separated state. Hence in this study we fabricated SDSC devices with different thicknesses of transparent TiO 2 nanotube array electrodes sensitized with Ru-(II)-donor-antenna dye and spiro-OMeTAD as a hole conductor. At AM 1.5 G, 100 mW/cm 2 illumination intensity, a power conversion efficiency of 1.94% was achieved when the TiO 2 nanotubes are initially subjected to TiCl 4 treatment. Furthermore, a linear increase in the cell current without loss in fill factor is observed for increasing length of TiO 2 nanotubes. The structural and morphological characteristics of the transparent TiO 2 nanotube arrays as well as the optimal conditions for the fabrication of SDSCs with transparent TiO 2 nanotubes on FTO glass are reported.

Isolation enhancement between two closely mounted antennas for indoor repeater systems

The effect of a frequency-selective surface (FSS) on enhancing the isolation between a donor and a coverage antenna for indoor WCDMA repeater antenna systems is presented.A unit cell of the proposed FSS consists of a half-wavelength resonator, an FR4 substrate, and a ground plane. Embedding it on the wall of each reflector for a donor and service antenna, the measured isolation enhancement is about 10 dB. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:697–700, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25806

Improving HSDPA Indoor Coverage and Throughput by Repeater and Dedicated Indoor System

The target of the paper is to provide guidelines for indoor planning and optimization using an outdoor-to-indoor repeater or a dedicated indoor system. The paper provides practical information for enhancing the performance of high-speed downlink packet access (HSDPA) in an indoor environment. The capabilities of an outdoor-to-indoor analog WCDMA repeater are set against a dedicated indoor system and, furthermore, compared to indoor coverage of a nearby macrocellular base station. An extensive measurement campaign with varying system configurations was arranged in different indoor environments. The results show that compared to dedicated indoor systems, similar HSDPA performance can be provided by extending macrocellular coverage inside buildings using an outdoor-to-indoor repeater. According to the measurements, the pilot coverage planning threshold of about −80 dBm ensures a 2500 kbps throughput for shared HSDPA connections. Improving the coverage above −80 dBm seems to provide only small advantage in HSDPA throughput. Of course, the pilot planning thresholds may change if different channel power allocations are used. In addition, network performance can be further improved by increasing the antenna density in the serving distributed antenna system. Finally, good performance of repeater implementation needs careful repeater gain setting and donor antenna siting.

A Compact On-Frequency Indoor Repeater Antenna with High Isolation for WCDMA Applications

In this paper, an indoor repeater antenna with high isolation for WCDMA application is proposed. The designed repeater has very small separation of 20 mm between the donor and server antennas. The antenna has two resonance frequencies to cover the WCDMA band from 1.92 GHz to 2.17 GHz. The fabricated antenna has VSWR below 1.5, gain over 8 dBi, and isolation between server and donor antennas less than -80 dB in the WCDMA band.

Highly Efficient Solar Cells using TiO2 Nanotube Arrays Sensitized with a Donor-Antenna Dye

Donor antenna dyes provide an exciting route to improving the efficiency of dye sensitized solar cells owing to their high molar extinction coefficients and the effective spatial separation of charges in the charge-separated state, which decelerates the recombination of photogenerated charges. Vertically oriented TiO(2) nanotube arrays provide an optimal material architecture for photoelectrochemical devices because of their large internal surface area, lower recombination losses, and vectorial charge transport along the nanotube axis. In this study, the results obtained by sensitizing TiO(2) nanotube arrays with the donor antenna dye Ru-TPA-NCS are presented. Solar cells fabricated using an antenna dye-sensitized array of 14.4 microm long TiO(2) nanotubes on Ti foil subjected to AM 1.5 one sun illumination in the backside geometry exhibited an overall conversion efficiency of 6.1%. An efficiency of 4.1% was obtained in the frontside illumination geometry using a 1 microm long array of transparent TiO(2) nanotubes subjected to a TiCl(4) treatment and then sensitized with the Ru-TPA-NCS dye. Open circuit voltage decay measurements give insight into the recombination behavior in antenna-dye sensitized nanotube photoelectrodes, demonstrating outstanding properties likely due to a reduction in the influence of the surface traps and reduced electron transfer from TiO(2) to ions in solution.

Key aspects of individual layers in solid-state dye-sensitized solar cells and novel concepts to improve their performance

In this feature article, we discuss the key aspects of solid-state dye-sensitized solar cells (SDSC) and propose different concepts based on extensive studies carried out in our group to improve their performance. The influence of compact TiO 2 layer, novel donor-antenna sensitizing dyes, nature of nanocrystalline-TiO 2 layers and solid-state organic hole conductors on the performance of SDSC is discussed in this article. Both preparation and thickness of the compact TiO 2 layer were optimized using spray pyrolysis. The studies revealed that an optimum film thickness of 120–150 nm of compact TiO 2 yielded the best rectifying behavior and SDSC performance. The influence of three different mesoporous titania films, obtained from three different titania nanocrystals, prepared by sol–gel, thermal, and colloidal-microwave process, was also studied and discussed here. The TiO 2 layer with the optimum pore volume and pore diameter (∼44 nm) displayed the highest efficiency and IPCE in SDSC. The importance of pore size rather than high surface area for filling the mesoporous layer with solid-state hole conductor became evident from this study. A series of heteroleptic Ru(II) complexes carrying donor antenna moieties, namely, triphenylamine (TPA) or N, N′-bis(phenyl)- N, N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD), were synthesized and applied in SDSC. These novel donor-antenna dyes revealed spectacular performances of power conversion efficiencies in the range 1.5–3.4%, as measured under AM 1.5 spectral conditions. This was attributed to highly efficient light harvesting of these novel dyes and the improved charge-transfer dynamics at TiO 2-dye and dye-hole conductor interfaces. Different low molecular weight and polymeric triphenyldiamines were synthesized and utilized as hole-transporting layers (HTL) in SDSC. Different studies showed that low molecular TPDs displayed better efficiency than polymeric counterparts due to their improved filling into the pores of nc-TiO 2 layer. Another interesting study revealed that an optimum driving force in terms of HOMO-level difference between the dye and HTL decides charge carrier generation efficiency. Recently, novel hole conductors with spiro-bifluorene-triphenylamine core for transporting holes and tetraethylene glycol side chains for binding lithium ions were synthesized and applied in SDSC. This work clearly emphasizes that Li +-salt is required at the TiO 2/dye interface as well as in the bulk of HTL. It was also found that the addition of about 5–20% of these Li +-binding hole conductors and higher Li-salt ( N-lithiotrifluoromethane sulfonamide) concentrations improved the SDSC performance. An improvement of about 120% in the solar cell efficiency as compared to the reference cells was achieved with an optimum composition of Li +-binding hole conductor and Li-salt.