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Abstract: Techniques of TiO2 film fabrication for dye-sensitized solar cells having a conversion efficiency of global air mass 1.5 (AM 1.5, 1000 W/m2) solar light to electric power over 10% are reported. Newly implemented fabrication technologies consist of pre-treatment of the working photoelectrode by TiCl4, variations in layer thickness of the transparent nanocrystalline-TiO2 and applying a topcoat light-scattering layer as well as the adhesion of an anti-reflecting film to the electrode''s surface. TiCl4 treatments induce improvements in the adhesion and mechanical strength of the nanocrystalline TiO2 layer. Optimization of the thickness of the TiO2 layer, acting as the working electrode, affects both the photocurrent and the photovoltage of the devices. Covering of the TiO2 photoanode by an anti-reflecting film results in enhancement of the photocurrent. Each of these components of film fabrication exerts a significant influence on the overall photovoltaic parameters of the devices resulting in improvements in the net energy conversion performance. [Copyright &y& Elsevier]

Abstract: We present a combined experimental and computational density functional theory (DFT)/time-dependent DFT study of the geometry, electronic structure and optical absorption spectrum of the solar-cell sensitizers cis-[Ru(4,4′-COO−-2,2′-bpy)2(X)2]4− (X=NCS, Cl) in water solution. The experimentally observed red-shift of the spectrum upon substitution of NCS-by Cl-is well reproduced by our theoretical model and appears to be related to stabilization of the t2g–π∗ HOMOs in the NCS− complex. The π∗ LUMOs of the Cl complex are destabilized by a smaller extent with respect to the HOMOs, due to the increased π-back bonding interactions with the bipyridine ligands. [Copyright &y& Elsevier]

The article focuses on the study about the role of sensitized protonation, which involves time-dependent density functional theory investigations on the excited states of ruthenium(II)-dye-sensitized titanium dioxide nanoparticles. The study confirms an injection mechanism for ruthenium(II) dyes on titanium dioxide mediated by the dye excited states and indicates a remarkable effect of dye protonation on the electronic properties of N719-sensitized titanium dioxide nanoparticles.

The article presents the study regarding the function of squaraine sensitizer. The synthesis, electronic and photovoltaic properties of the squaraine sensitizer had been determined using synthetic strategy which yielded with very high incident monochromatic photon-to-current conversion. Making directionality and inhibiting self-quenching of the sensitizer are the key for unprecedented efficiency of squaraines.

The power conversion efficiency of perovskite solar cells continues to increase. However, defects in perovskite materials are detrimental to their carrier dynamics and structural stability, ultimately limiting the photovoltaic characteristics and stability of perovskite solar cells. Herein, we report that 6H polytype perovskite effectively engineers defects at the interface with cubic polytype FAPbI 3 , which facilitates radiative recombination and improves the stability of the polycrystalline film. We particularly show the detrimental effects of shallow-level defect that originates from the formation of the most dominant iodide vacancy (V I + ) in FAPbI 3 . Furthermore, additional surface passivation on top of the hetero-polytypic perovskite film results in an ultra-long carrier lifetime exceeding 18 μs, affords power conversion efficiencies of 24.13% for perovskite solar cells, 21.92% (certified power conversion efficiency: 21.44%) for a module, and long-term stability. The hetero-polytypic perovskite configuration may be considered as close to the ideal polycrystalline structure in terms of charge carrier dynamics and stability., (© 2024. The Author(s).)

Two thiocyanate-free ruthenium(II) sensitizers, TFRS-41 and TFRS-42, with distinctive dialkoxyphenyl thienyl substituents were successfully prepared and tested for potential applications in making dye-sensitized solar cells (DSCs). Subsequent device fabrication was conducted by using a [Co(bpy)3 ](2+/3+) -based (bpy=2,2'-bipyridine) electrolyte, for which the best performance data, namely, JSC =13.11 mA cm(-2) , VOC =862 mV, fill factor=0.771, and η=8.71%, were recorded for the sensitizer TFRS-42 with a 2,6-dialkoxyphenyl substituent under AM 1.5G irradiation. The markedly higher Voc value was confirmed by the longer electron lifetime revealed in transient photovoltage (TPV) measurements versus the TFRS-1 sensitizer. In addition, DFT calculation and detailed first-principles computational analysis were conducted to provide a rationale for the observed trends in their photovoltaic performances and electron lifetimes, with reference to different performances exhibited by three thiocyanate-free sensitizers, TFRS-1, TFRS-41 and TFRS-42, versus Z907 reference. Through the proper control of peripheral substituents, the thiocyanate-free ruthenium(II)-based DSC sensitizers can positively influence the performances of DSCs, with better light-harvesting capability and suppressed charge recombination, for DSC cells fabricated by using a [Co(bpy)3 ](2+/3+) -based electrolyte., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Novel star-shaped hole transporting materials with a triazine unit have been synthesized. When the new Triazine-Th-OMeTPA was used as a hole transporting material in perovskite solar cells, the power conversion efficiency reached 12.51% under AM 1.5 G (100 mW cm(-2)) illumination, showing competitive photovoltaic performance with the widely used spiro-OMeTAD based solar cell (13.45%).

Coordination of bidentate 5-pentafluorophenyldipyrrinate (pfpdp) or 5-(2-thienyl)dipyrrinate (2-tdp) to a Ru(II) center bearing 2,2':6',2″-terpyridine-4,4',4″-tricarboxylate (tctpy) and a NCS(-) ligand results in strongly light-absorbing complexes [Ru(tctpy)(L)(NCS)] (L = pfpdp or 2-tdp). Anchored to a mesoporous TiO2 electrode, these complexes afford a photoaction spectral response at wavelengths of up to 950 nm, one of the most red-shifted values reported to date for molecular dyes in the dye-sensitized solar cell (DSSC).

A new phthalocyanine (Pc) bearing bulky peripheral substituents and a carboxylic anchoring group directly attached to the macrocycle has been prepared and used as a sensitizer in DSSCs, reaching 5.57% power conversion efficiency. In addition, an enhanced performance for the TT40 dye, previously reported by us, was achieved in optimized devices, obtaining a new record efficiency with Pc-sensitized cells., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mesoporous TiO2 nanoparticle films are used as photoanodes for high-efficiency dye-sensitized solar cells (DSCs). In spite of excellent photovoltaic power conversion efficiencies (PCEs) displayed by titanium dioxide nanoparticle structures, the transport rate of electrons is known to be low due to low electron mobility. So the alternate oxides, including ZnO, that possesses high electron mobility are being investigated as potential candidates for photoanodes. However, the PCE with ZnO is still lower than with TiO2, and this is typically attributed to the low internal surface area. In this work, we attempt to make a one-to-one comparison of the photovoltaic performance and the electron transfer dynamics involved in DSCs, with ZnO and TiO2 as photoanodes. Previously such comparative investigations were hampered due to the morphological differences (internal surface area, pore diameter, porosity) that exist between zinc oxide and titanium dioxide films. We circumvent this issue by depositing different thicknesses of these oxides, by atomic layer deposition (ALD), on an arbitrary mesoporous insulating template and subsequently using them as photoanodes. Our results reveal that at an optimal thickness ZnO exhibits photovoltaic performances similar to TiO2, but the internal electron transfer properties differ. The higher photogenerated electron transport rate contributed to the performances of ZnO, but in the case of TiO2, it is the low recombination rate, higher dye loading, and fast electron injection.

We report the use of Y(3+)-substituted TiO2 (0.5%Y-TiO₂) in solid-state mesoscopic solar cells, consisting of CH₃NH₃PbI₃ as the light harvester and spiro-OMeTAD as the hole transport material. A power conversion efficiency of 11.2% under simulated AM 1.5 full sun illumination was measured. A 15% improvement in the short-circuit current density was obtained compared with pure TiO₂, due to the effect of Y(3+) on the dimensions of perovskite nanoparticles formed on the semiconductor surface, showing that the surface modification of the semiconductor is an effective way to improve the light harvesters' morphology and electron transfer properties in the solid-state mesoscopic solar cells.

Four new heteroleptic iridium(III) complexes in the family [Ir(dfppz)(2)(N^N)](+), where Hdfppz = 1-(2,4-difluorophenyl)-1H-pyrazole and N^N = 6-phenyl-2,2'-bipyridine (1), 4,4'-(di-tert-butyl)-6-phenyl-2,2'-bipyridine (2), 4,4'-(di-tert-butyl)-6,6'-diphenyl-2,2'-bipyridine (3) and 4,4'-bis(dimethylamino)-2,2'-bipyridine (4), have been synthesized as the hexafluoridophosphate salts and fully characterized. Single crystal structures of ligand 3 and the precursor [Ir(2)(dfppz)(4)(μ-Cl)(2)] have been determined, along with the structures of the complexes 4{[Ir(dfppz)(2)(1)][PF(6)]}·3CH(2)Cl(2), [Ir(dfppz)(2)(3)][PF(6)]·CH(2)Cl(2) and [Ir(dfppz)(2)(4)][PF(6)]·CH(2)Cl(2). The role of inter- and intramolecular face-to-face π-stacking in the solid state is discussed. In the [Ir(dfppz)(2)(N^N)](+) (N^N = 1-3) cations, the phenyl substituent in ligands 1, 2 or 3 undergoes hindered rotation on the NMR timescale at 298 K in solution and the systems have been studied by variable temperature NMR spectroscopy. Acetonitrile solutions of [Ir(dfppz)(2)(N^N)][PF(6)] (N^N = 1-3) exhibit similar absorption spectra arising from ligand-based transitions; absorption intensity is enhanced on going to [Ir(dfppz)(2)(4)][PF(6)] and the spectrum extends further into the visible region. Acetonitrile solutions of the complexes are blue emitters with λ(em) = 517, 505, 501 and 493 nm for N^N = 1, 2, 3 and 4, respectively (λ(exc) = 280-310 nm). The redox behaviours of [Ir(dfppz)(2)(N^N)][PF(6)] (N^N = 1-3) are similar, and the introduction of the electron-donating NMe(2) substituents onto the N^N ligand shifts the metal-centred oxidation to less positive potentials. Theoretical calculations predict a mixed metal-to-ligand/ligand-to-ligand charge transfer (MLCT/LLCT) character for the emitting triplet state in agreement with the broad and unstructured character of the emission bands. The NMe(2) substituents enlarge the HOMO-LUMO gap and blue-shifts the emission of [Ir(dfppz)(2)(4)](+) that is centred on the ancillary ligand. These complexes, when processed into a thin film and sandwiched between two electrodes, lead to very low voltage operating electroluminescent devices. No additional components are needed, which demonstrates their electron and hole transport abilities in conjunction with the luminescent properties.

A novel, asymmetric DPP bridge/core was synthesized and tested in DSC devices. By desymmetrising the DPP core/bridge, a remarkable IPCE of >80% and a maximum power conversion efficiency of 7.7% were achieved. With the use of a wide-bandgap co-sensitizer, 8.6% PCE was realized under standard AM1.5G sunlight.

We report herein lightweight, and economical dye-sensitized solar cells fabrication facilitated by an all plastic, metal free cathode consisting of poly(3,4-ethylenedioxythiophene).

Zinc(II) phthalocyanine dyes that contain triarylamine-terminated bisthiophene and hexylbisthiophene groups have been synthesized by a convergent approach by using carboxytriiodo-ZnPc as a precursor. Further transformation of the iodo groups by a Pd-catalyzed reaction allowed easy preparation of further extended π-conjugated carboxy-ZnPcs. These dyes have been used as sensitizers in dye-sensitized solar cells, which exhibit a panchromatic response and moderate overall efficiencies., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Acceptor motifs based on nitrogen containing heterocycles have been synthesized for use in dye-sensitized solar cells (DSCs). Through the selective addition of nitrogen atoms and increased conjugation of the nitrogen containing heterocycles the excited-state oxidation potential, E((S+/S*)), may be conveniently tuned with minimal effect on the ground-state oxidation potential, E((S+/S)), of the dye., (This journal is © The Royal Society of Chemistry 2012)

We report new bis-cyclometalated cationic iridium(III) complexes [(C(^)N)(2)Ir(CN-tert-Bu)(2)](CF(3)SO(3)) that have tert-butyl isocyanides as neutral auxiliary ligands and 2-phenylpyridine or 2-(4'-fluorophenyl)-R-pyridines (where R is 4-methoxy, 4-tert-butyl, or5-trifluoromethyl) as C(^)N ligands. The complexes are white or pale yellow solids that show irreversible reduction and oxidation processes and have a large electrochemical gap of 3.58-3.83 V. They emit blue or blue-green phosphorescence in liquid/solid solutions from a cyclometalating-ligand-centered excited state. Their emission spectra show vibronic structure with the highest-energy luminescence peak at 440-459 nm. The corresponding quantum yields and observed excited-state lifetimes are up to 76% and 46 μs, respectively, and the calculated radiative lifetimes are in the range of 46-82 μs. In solution, the photophysical properties of the complexes are solvent-independent, and their emission color is tuned by variation of the substituents in the cyclometalating ligand. For most of the complexes, an emission color red shift occurs in going from solution to neat solids. However, the shift is minimal for the complexes with bulky tert-butyl or trifluoromethyl groups on the cyclometalating ligands that prevent aggregation. We report the first example of an iridium(III) isocyanide complex that emits blue phosphorescence not only in solution but also as a neat solid.

We report the application of spectroelectrochemical techniques to compare the hole percolation dynamics of molecular networks of two ruthenium bipyridyl complexes adsorbed onto mesoporous, nanocrystalline TiO(2) films. The percolation dynamics of the ruthenium complex cis-di(thiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylic acid)-(2,2'-bipyridyl-4,4'-tridecyl) ruthenium(II), N621, is compared with those observed for an analogous dye with an additional tri-phenyl amine (TPA) donor moiety, cis-di(thiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylic acid)-(2,2'-bipyridyl-4,4'-bis(vinyltriphenylamine)) ruthenium(II), HW456. The in situ oxidation of these ruthenium complexes adsorbed to the TiO(2) films is monitored by cyclic voltammetry and voltabsorptometry, whilst the dynamics of hole (cation) percolation between adsorbed ruthenium complexes is monitored by potentiometric spectroelectrochemistry and chronoabsorptometry. The hole diffusion coefficient, D(eff), is shown to be dependent on the dye loading on the nanocrystalline TiO(2) film, with a threshold observed at ∼60% monolayer surface coverage for both dyes. The hole diffusion coefficient of HW456 is estimated to be 2.6 × 10(-8) cm(2)/s, 20-fold higher than that obtained for the control N621, attributed to stronger electronic coupling between the TPA moieties of HW456 accelerating the hole percolation dynamics. The presence of mercuric ions, previously shown to bind to the thiocyanates of analogous ruthenium complexes, resulted in a quenching of the hole percolation for N621/TiO(2) films and an enhancement for HW456/TiO(2) films. These results strongly suggest that the hole percolation pathway is along the overlapped neighbouring -NCS groups for the N621 molecules, whereas in HW456 molecules cation percolation proceeds between intermolecular TPA ligands. These results are discussed in the context of their relevance to the process of dye regeneration in dye sensitised solar cells, and to the molecular wiring of wide bandgap inorganic materials for battery and sensing applications.

Following former studies, the donor-acceptor combinations of -NH(2)-substituted porphyrin donor and the acceptors C, D, E, F, H and G, those of -OH-, -CH(3)- and -Ph-substituted porphyrins as well as porphine donors and the acceptors E, G, and H, and those of -F- and -SH-substituted porphyrin donors and the acceptor G as novel sensitizer candidates have been designed and calculated at the density functional B3LYP level. The result shows that -NH(2)-, -OH- and -CH(3)-substituted porphyrins as donors combined with the acceptor G are very promising to provide good performances as sensitizers because of their smaller HOMO-LUMO gaps, much red-shifted absorption bands, and good frontier molecular orbital spatial distributions. They are all promising to challenge the current photon-to-current conversion efficiency record 7.1% of porphyrin-sensitized solar cells in which the -NH(2)-substituted porphyrins as donors combined with the acceptor G are the best systems.

A series of unsymmetrical zinc phthalocyanines bearing an anchoring carboxylic function linked to the phthalocyanine ring through different spacers were designed for dye-sensitised solar cells (DSSC). The modification of the spacer group allows not only a variable distance between the dye and the nanocrystalline TiO(2), but also a distinct orientation of the phthalocyanine on the semiconductor surface. The photovoltaic data show that the nature of the spacer group plays a significant role in the electron injection from the photo-excited dye into the nanocrystalline TiO(2) semiconductor, the recombination rates and the efficiency of the cells. The incident monochromatic photon-to-current conversion efficiency (IPCE) for phthalocyanines bearing an insulating spacer is as low as 9%, whereas for those with a conducting spacer an outstanding IPCE 80% was obtained.

The influence of oxygen on various ophthalmologic complications is not completely understood and intraocular oxygen measurements are essential for better diagnosis and treatment. A magnetically controlled wireless sensor device is proposed for minimally invasive intraocular oxygen concentration measurements. This device will make it possible to make measurements at locations that are currently too invasive for human intervention by integrating a luminescence optical sensor and a magnetic steering system. The sensor works based on quenching of luminescence in the presence of oxygen. A novel iridium phosphorescent complex is designed and synthesized for this system. A frequency-domain lifetime measurement approach is employed because of the intrinsic nature of the lifetime of luminescence. Experimental results of the oxygen sensor are presented to demonstrate the concept. In order to use this sensor for in vivo intraocular applications, the size of the sensor must be reduced, which will require an improved signal-to-noise ratio.