Effects of Core‐modification on Porphyrin Sensitizers to the Efficiencies of Dye‐sensitized Solar Cells

To study dye‐sensitized solar cells (DSSCs) with core‐modified porphyrins as the sensitizing dyes, three porphyrins with an ethynyl benzoic acid as an anchoring group are prepared. The properties of free‐base regular porphyrin (N4), thiaporphyrin (N3S) and oxaporphyrin (N3O) were thoroughly studied by spectroscopic methods, DFT calculations, and photovoltaic measurements. Replacing one of the porphyrinic core nitrogen atoms by oxygen or sulfur considerably changes the absorption spectra. The Soret band of the N3O and N3S observed bathochromic shifts of 3‐9 nm while the Q band reaches 700 nm to the near‐infrared region. The overall conversion efficiencies of the DSSCs based on these porphyrins are in the order N4 (3.66%) ? N3S (0.22%) > N3O (0.01%). The time‐correlated single photon counting observed short fluorescence lifetimes for N3O adsorbed both on TiO₂ and Al₂O₃ which explicates the poor efficiency of DSSC using N3O as the photosensitizer.     

Low‐Symmetry Ω‐Shaped Zinc Phthalocyanine Sensitizers with Panchromatic Light‐Harvesting Properties for Dye‐Sensitized Solar Cells

Two low‐symmetry phthalocyanines (Pcs) substituted with thiophene units at the non‐peripheral (α) and peripheral (β) positions were synthesized and their optical, electronic‐structure, and electrochemical properties were investigated. The substitution of thiophene units at the α positions of the phthalocyanine skeleton resulted in a red shift of the Q band and significantly modified the molecular‐orbital electronic distributions just below the HOMO and just above the LUMO, with distortion of the typical Gouterman four‐orbital arrangement of MOs. Two amphiphilic Ω‐shaped ZnPcs ( αPcS1 and αPcS2 ) bearing a π‐conjugated side chain with an adsorption site at an α position of the Pc macrocycle were synthesized as sensitizers for dye‐sensitized solar cells (DSSCs). The absorption spectra of αPcS1 and αPcS2 showed red shifted Q bands and a broad band from 350 to 550 nm assignable to the intramolecular charge‐transfer transition from the ZnPc core to the side chains. Time‐dependent DFT calculations provided a clear interpretation of the effect of the thiophene conjugation on the typical phthalocyanine core π MOs. Compound αPcS1 was used as a light‐harvesting dye on a TiO₂ electrode for a DSSC, which showed a panchromatic response in the range 400–800 nm with a power conversion efficiency of 5.5 % under one‐sun conditions.     

An Interconnected Ternary MIn2S4 (M=Fe,Co, Ni) Thiospinel Nanosheet Array: A Type of Efficient Platinum‐Free Counter Electrode for Dye‐Sensitized Solar Cells

The ternary iron‐group thiospinels of metal diindium sulfides (MIn₂S₄, M=Fe, Co, Ni) with a vertically aligned nanosheet array structure are fabricated through an in situ solvothermal method on F‐doped tin oxide (FTO) substrates, which are employed as one type of platinum (Pt)‐free counter electrodes (CEs) in structure‐dependent dye‐sensitized solar cells (DSSCs). A DSSC assembled with ternary CoIn₂S₄ CE achieves an photoelectric conversion efficiency (PCE) of 8.83 %, outperforming than that of FeIn₂S₄ (7.18 %) and NiIn₂S₄ (8.27 %) CEs under full sunlight illumination (100 mW cm⁻², AM 1.5 G), which is also comparable with that of the Pt CE (8.19 %). Putting aside that the interconnected nanosheet array provides fast electron transfer and electrolyte diffusion channels, the highest PCE of CoIn₂S₄ based DSSC results from its largest specific surface area (144.07 m² g⁻¹), providing abundant active sites and the largest electron injection efficiency from CE to electrolyte.     

Enhancement of photocurrent of polymer‐gelled dye‐sensitized solar cell by incorporation of exfoliated montmorillonite nanoplatelets

Poly(n‐isopropylacrylamide) (PNIPAAm) and its nanocomposite with exfoliated montmorillonite (MMT) were prepared by soap‐free emulsion polymerization and individually applied to gel the electrolyte systems for the dye‐sensitized solar cells (DSSCs). Each exfoliated MMT nanoplatelet had a thickness of ～ 1 nm, carried ～ 1.8 cation/nm², and acted like a two‐dimensional electrolyte. The DSSC with the LiI/I₂/tertiary butylpyridine electrolyte system gelled by this polymer nanocomposite had higher short‐circuit current density (J_sc) compared to that gelled by the neat PNIPAAm. The former has a J_sc of 12.6 mA/cm², an open circuit voltage (V_oc) of 0.73 V, and a fill factor (FF) of 0.59, which harvested 5.4% electricity conversion efficiency (η) under AM 1.5 irradiation at 100 mW/cm², whereas the latter has J_sc = 7.28 mA/cm², V_oc = 0.72 V, FF = 0.60, and η = 3.17%. IPCE of the nanocomposite‐gelled DSSC were also improved. Electrochemical impedance spectroscopy of the DSSCs revealed that the nanocomposite‐gelled electrolytes significantly decreased the impedances in three major electric current paths of DSSCs, that is, the resistance of electrolytes and electric contacts, impedance across the electrolytes/dye‐coated TiO₂ interface, and Nernstian diffusion within the electrolytes. The results were also consistent with the increased molar conductivity of nanocomposite‐gelled electrolytes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 47–53, 2008     

Non‐classical Design of High‐Efficiency Sensitizers for Dye‐Sensitized Solar Cells

The dye regeneration step in a dye‐sensitized solar cell (DSSC) affects significantly the device efficiency. To be able to predict the dye regeneration efficiency by the electrolyte this paper provides a facile way to design high‐efficiency sensitizers for DSSC. This paper proposes, for the first time, a simple and ingenious way to identify the dye regeneration sites and their relative efficiencies when a specific electrolyte is used. Two steps are proposed to identify the dye regeneration sites and their relative regeneration efficiencies: (1) drawing all the resonance structures of the oxidized dye to determine the regeneration sites, and (2) choosing the most favored site for dye regeneration as the chemically softest (when the redox couple used is soft I⁻/I₃⁻ pair) and the least spatially hindered site. The regeneration sites identified by the resonance structures are consistent with the β‐LUSO (β lowest unoccupied spin orbital) distribution, which is generally used for identifying the dye regeneration sites, calculated with DT‐DFT theory. The relative dye regeneration efficiency and photovoltaic performance of both ruthenium and metal‐free organic dyes predicted by the method reported here are supported by experimental data and the proposed dye regeneration mechanism. Several types of dye molecules are used to demonstrate the correctness of this new tool. This non‐classical tool, which uses the well‐known chemical knowledge of the resonance structure and hard–soft acid–base principle, without any computer calculation or physicochemical measurement, provides a very simple and powerful tool to quickly conceive high‐efficiency sensitizers for DSSCs.     

Investigation of excited‐state properties of fluorene–thiophene oligomers by the SAC‐CI theoretical approach

Excited states of fluorene‐ethylenedioxythiophene (FEDOT) and fluorene‐S,S‐dioxide‐thiophene (FTSO2) monomers and dimers were studied by the symmetry‐adapted cluster (SAC)‐configuration interaction (CI) method. The absorption and emission peaks observed in the experimental spectra were theoretically assigned. The first three excited states of the optimized conformers, and the conformers of several torsional angles, were computed by SAC‐CI/D95(d). Accurate absorption spectra were simulated by taking the thermal average for the conformers of torsional angles from 0° to 90°. The conformers of torsional angles 0°, 15°, and 30° mainly contributed to the absorption spectra. The full width at half‐maximum of the FEDOT absorption band is 0.60 eV (4839 cm^?1), which agrees very well with the experimental value of 0.61 eV (4900 cm^?1). The maximum absorption wavelength is located at 303 nm, which is close to those of the experimental band (327 nm). The calculated absorption spectrum of FTSO2 showed two bands in the range of 225–450 nm. This agrees very well with the available experimental spectrum of a polymer of FTSO2, where two bands are detected. The excited‐state geometries were investigated by CIS/6‐31G(d). These showed a quinoid‐type structure which exhibited a shortening of the inter‐ring distance (0.06 Å for FEDOT and 0.04 Å for FTSO2). The calculated emission energy of FEDOT is 3.43 eV, which agrees very well with the available experimental data (3.46 eV). The fwhm_E is about 0.49 eV (3952 cm^?1), while the experimental fwhm is 0.43 eV (3500 cm^?1). For FTSO2, two bands were also found in the emission spectrum. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Synthesis and Infrared Multi‐band Absorption Properties of Core‐shell NaYF4:Yb3+, Er3+@SiO2 Nanoparticles

Due to the unique size effects, nanomaterials in infrared absorption have attracted much attention for their strong absorption in the infrared region. To achieve the infrared multi‐band absorption, we propose to synthesize a core‐shell structure nanomaterial consisting of NaYF₄:Yb³⁺, Er³⁺ core and a layer of SiO₂ as shell. A series of NaYF₄:Yb³⁺, Er³⁺ nanocrystals were synthesized through hydrothermal method by adjusting the ratio of citric acid(CA)‐to‐NaOH, and the effects of CA concentration, and NaOH concentration were studied in detail. NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanoparticles were synthesized by sol‐gel method using TEOS as silica source. The results show that the core‐shell NaYF₄:Yb³⁺, Er³⁺@SiO₂ nanoparticles were successfully synthesized. Up‐conversion spectra of these nanoparticles were recorded with 980 nm laser excitation under room temperature. There are no changes of the emission centers of nanoparticles before or after silica coating, but the emission intensities of nanoparticles after silica coating are weakened. Furthermore, the property of infrared multi‐band absorption was tested through ultraviolet‐visible‐near infrared spectrophotometer and infrared absorption spectra. The results illustrate that the multi‐band infrared absorption nanomaterial was successfully synthesized.     

Synthesis and characterization of cross‐linkable ruthenium complex dye and its application on dye‐sensitized solar cells

A new crosslinkable light sensitizer, Ru(2,2′‐bipyridine‐4,4′‐bicarboxylic acid)(4,4′‐bis(11‐dodecenyl)‐2,2′‐bipyridine)(NCS)₂, denoted as Ru‐C for titanium oxide nanocrystalline‐based solar cells was synthesized with its crosslinking properties invesitigated by Fourier‐transform infrared and UV‐vis absorption spectroscopies. After crosslinking by itself or copolymerizing with methyacrylic acid, their sensitized solar cells with poly(methylacrylate)‐gelled electrolyte system not only attained more than 5% of power conversion efficiency at AM 1.5 illumination (100 mW/cm²), but also gave rise to long storage life. To the best our knowledge, this is the first crosslinkable dye ever applied to the DSSC in the literature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 366–372, 2010     

A High‐Voltage Molecular‐Engineered Organic Sensitizer–Iron Redox Shuttle Pair: 1.4 V DSSC and 3.3 V SSM‐DSSC Devices

The development of high voltage solar cells is an attractive way to use sunlight for solar‐to‐fuel devices, multijunction solar‐to‐electric systems, and to power limited‐area consumer electronics. By designing a low‐oxidation‐potential organic dye ( RR9 )/redox shuttle (Fe(bpy)₃^3+/2+) pair for dye‐sensitized solar‐cell (DSSC) devices, the highest single device photovoltage (1.42 V) has been realized for a DSSC not relying on doped TiO₂. Additionally, Fe(bpy)₃^3+/2+ offers a robust, readily tunable ligand platform for redox potential tuning. RR9 can be regenerated with a low driving force (190 mV), and by utilizing the RR9 /Fe(bpy)₃^3+/2+ redox shuttle pair in a subcell for a sequential series multijunction (SSM)‐DSSC system, one of the highest known three subcell photovoltage was attained for any solar‐cell technology (3.34 V, >1.0 V per subcell).     

Quasi‐solid‐state dye‐sensitized solar cells containing P (MMA‐co‐AN)‐based polymeric gel electrolyte

Quasi‐solid state dye‐sensitized solar cells (QS‐DSSC) containing poly (methyl methacrylate‐co‐acrylonitrile) [P (MMA‐co‐AN)] gel electrolytes were fabricated. By tuning AN molar percentage in P (MMA‐co‐AN), the optimized polymeric gel electrolyte for fabricating QS‐DSSC can be obtained. QS‐DSSC containing polymeric gel electrolyte with 45 mol.% AN in P(MMA‐co‐AN) shows higher energy conversion efficiency than that of QS‐DSSCs containing polymeric gel electrolytes with either pure PMMA or PAN. So it presents an effective way to improve the photovoltaic performance of QS‐DSSC by tuning the components of polymeric gelling agent. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of organic sulfobetaine‐based polymer gel electrolyte for dye‐sensitized solar cell application

We have synthesized eco‐friendly, economic, and equally efficient polysulfobetaine‐based gel electrolyte to the alternative of liquid electrolyte in the fabrication of dye‐sensitized solar cells (DSSCs) for the first time. This nitrogen‐rich and highly conductive polysulfobetaine was synthesized by an easy and facile method without the use of any catalyst and explored for its DSSC application. The synthesized polymer gel electrolyte exhibited good ionic conductivity about 6.8 × 10^?3 Scm^?1 at ambient temperatures. DSSCs were fabricated based on this polysulfobetaine gel electrolyte and studied for their performance based on photovoltaic parameters. The DSSC photovoltaic results were appreciable and are Voc = 0.82 V, Jsc = 11.49 mA/cm², FF = 66%, and PCE = 6.26% at 1 sun intensity. These values are slightly lower than conventional liquid electrolyte‐based DSSC shown as Voc = 0.78 V, Jsc = 12.90 mA/cm², FF = 69%, and PCE = 7.07%, both at 100 mWcm^?2. Conductivity and photovoltaic parameters of the device reveals that as prepared polysulfobetaine‐based polymer gel electrolyte may be useful in the fabrication of DSSC and other electrochemical devices. Copyright © 2017 John Wiley & Sons, Ltd.     

Probing the Electronic Structure and Photoactivation Process of Nitrogen‐Doped TiO2 Using DRS,PL, and EPR

The electronic structure and photoactivation process in N‐doped TiO₂ is investigated. Diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and electron paramagnetic resonance (EPR) are employed to monitor the change of optical absorption ability and the formation of N species and defects in the heat‐ and photoinduced N‐doped TiO₂ catalyst. Under thermal treatment below 573 K in vacuum, no nitrogen dopant is removed from the doped samples but oxygen vacancies and Ti³⁺ states are formed to enhance the optical absorption in the visible‐light region, especially at wavelengths above 500 nm with increasing temperature. In the photoactivation processes of N‐doped TiO₂, the DRS absorption and PL emission in the visible spectral region of 450–700 nm increase with prolonged irradiation time. The EPR results reveal that paramagnetic nitrogen species (N_s^.), oxygen vacancies with one electron (V_o^.), and Ti³⁺ ions are produced with light irradiation and the intensity of N_s^. species is dependent on the excitation light wavelength and power. The combined characterization results confirm that the energy level of doped N species is localized above the valence band of TiO₂ corresponding to the main absorption band at 410 nm of N‐doped TiO₂, but oxygen vacancies and Ti³⁺ states as defects contribute to the visible‐light absorption above 500 nm in the overall absorption of the doped samples. Thus, a detailed picture of the electronic structure of N‐doped TiO₂ is proposed and discussed. On the other hand, the transfer of charge carriers between nitrogen species and defects is reversible on the catalyst surface. The presence of oxygen‐vacancy‐related defects leads to quenching of paramagnetic N_s^. species but they stabilize the active nitrogen species N_s^?.     

Doubly N‐Confused Calix[6]phyrin Bis‐Organopalladium Complexes: Photostable Triplet Sensitizers for Singlet Oxygen Generation

Triplet photosensitizers that generate singlet oxygen efficiently are attractive for applications such as photodynamic therapy (PDT). Extending the absorption band to a near‐infrared (NIR) region (700 nm≈) with reasonable photostability is one of the major demands in the rational design of such sensitizers. We herein prepared a series of mono‐ and bis‐palladium complexes ( 1‐Pd‐H₂ , 2‐Pd‐H₂ , 1‐Pd‐Pd , and 2‐Pd‐Pd ) based on modified calix[6]phyrins as photosensitizers for singlet oxygen generation. These palladium complexes showed intense absorption profiles in the visible‐to‐NIR region (500–750 nm) depending on the number of central metals. Upon photoirradiation in the presence of 1,5‐dihydroxynaphthalene (DHN) as a substrate for reactive oxygen species, the bis‐palladium complexes generated singlet oxygen with high efficiency and excellent photostability. Singlet oxygen generation was confirmed from the characteristic spectral feature of the spin trapped complex in the EPR spectrum and the intact ¹O₂ emission at 1270 nm.     

BiVO4‐TiO2 Composite Photocatalysts for Dye Degradation Formed Using the SILAR Method

Composite photocatalyst films have been fabricated by depositing BiVO₄ upon TiO₂ via a sequential ionic layer adsorption reaction (SILAR) method. The photocatalytic materials were investigated by XRD, TEM, UV/Vis diffuse reflectance, inductively coupled plasma optical emission spectrometry (ICP‐OES), XPS, photoluminescence and Mott–Schottky analyses. SILAR processing was found to deposit monoclinic‐scheelite BiVO₄ nanoparticles onto the surface, giving successive improvements in the films′ visible light harvesting. Electrochemical and valence band XPS studies revealed that the prepared heterojunctions have a type II band structure, with the BiVO₄ conduction band and valence band lying cathodically shifted from those of TiO₂. The photocatalytic activity of the films was measured by the decolourisation of the dye rhodamine 6G using λ>400 nm visible light. It was found that five SILAR cycles was optimal, with a pseudo‐first‐order rate constant of 0.004 min^?1. As a reference material, the same SILAR modification has been made to an inactive wide‐band‐gap ZrO₂ film, where the mismatch of conduction and valence band energies disallows charge separation. The photocatalytic activity of the BiVO₄–ZrO₂ system was found to be significantly reduced, highlighting the importance of charge separation across the interface. The mechanism of action of the photocatalysts has also been investigated, in particular the effect of self‐sensitisation by the model organic dye and the ability of the dye to inject electrons into the photocatalyst′s conduction band.     

SrTiO3/TiO2 Hybridstructure as Photoanode in Dye‐Sensitized Solar Cell

In dye‐sensitized solar cells (DSSCs), the charge recombination at the TiO₂/dye/electrolyte interface greatly influences the photoelectron conversion efficiency. Hybrid semiconductor materials with matched band potentials are designed to reduce the charge recombination. In this study, SrTiO₃/TiO₂ hybridstructure was synthesized by using TiO₂ nanoparticles as template in a hydrothermal, showing a negative shift in the flat band potential. The DSSC with the SrTiO₃/TiO₂ anode exhibits an increased photovoltage and a reduced photocurrent. The suppression of charge recombination at the TiO₂/dye/electrolyte interface was observed in the electrochemical impedance spectroscopy, causing an improvement in the photovoltage. However, the SrTiO₃/TiO₂ system shows an obstructed electrons injection from the dye to SrTiO₃/TiO₂, limiting the photocurrent performance. The photoelectrochemical properties of the SrTiO₃/TiO₂ system are discussed in detail herein.     

Highly Catalytic Carbon Nanotube/Pt Nanohybrid‐Based Transparent Counter Electrode for Efficient Dye‐Sensitized Solar Cells

Low‐cost transparent counter electrodes (CEs) for efficient dye‐sensitized solar cells (DSSCs) are prepared by using nanohybrids of carbon nanotube (CNT)‐supported platinum nanoparticles as highly active catalysts. The nanohybrids, synthesized by an ionic‐liquid‐assisted sonochemical method, are directly deposited on either rigid glass or flexible plastic substrates by a facile electrospray method for operation as CEs. Their electrochemical performances are examined by cyclic voltammetry, current density–voltage characteristics, and electrochemical impedance spectroscopy (EIS) measurements. The CNT/Pt hybrid films exhibit high electrocatalytic activity for I^?/I₃^? with a weak dependence on film thickness. A transparent CNT/Pt hybrid CE film about 100 nm thick with a transparency of about 70 % (at 550 nm) can result in a high power conversion efficiency (η) of over 8.5 %, which is comparable to that of pyrolysis platinum‐based DSSCs, but lower cost. Furthermore, DSSC based on flexible CNT/Pt hybrid CE using indium‐doped tin oxide‐coated polyethylene terephthalate as the substrate also exhibits η=8.43 % with J_sc=16.85 mA cm^?2, V_oc=780 mV, and FF=0.64, and this shows great potential in developing highly efficient flexible DSSCs.     

High‐Performance Platinum‐Free Dye‐Sensitized Solar Cells with Molybdenum Disulfide Films as Counter Electrodes

By using a radio‐frequency sputtering method, we synthesized large‐area, uniform, and transparent molybdenum disulfide film electrodes (1, 3, 5, and 7 min) on transparent and conducting fluorine‐doped tin oxide (FTO), as ecofriendly, cost‐effective counter electrodes (CE) for dye‐sensitized solar cells (DSSCs). These CEs were used in place of the routinely used expensive platinum CEs for the catalytic reduction of a triiodide electrolyte. The structure and morphology of the MoS₂ was analyzed by using Raman spectroscopy, X‐ray diffraction, and X‐ray photoemission spectroscopy measurements and the DSSC characteristics were investigated. An unbroken film of MoS₂ was identified on the FTO crystallites from field‐emission scanning electron microscopy. Cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel curve measurements reveal the promise of MoS₂ as a CE with a low charge‐transfer resistance, high electrocatalytic activity, and fast reaction kinetics for the reduction of triiodide to iodide. Finally, an optimized transparent MoS₂ CE, obtained after 5 min synthesis time, showed a high power‐conversion efficiency of 6.0 %, which comparable to the performance obtained with a Pt CE (6.6 %) when used in TiO₂‐based DSCCs, thus signifying the importance of sputtering time on DSSC performance.     

Treatment of TiO2 with COOH‐Functionalized Germanium Nanoparticles to Enhance the Photocurrent of Dye‐Sensitized Solar Cells

A dye‐sensitized solar cell (DSSC) containing a TiO₂ film treated with COOH‐functionalized germanium nanoparticles (Ge COOH Nps) exhibited a higher short‐circuit photocurrent density (J_sc; 15.4 mA cm⁻²) compared to the corresponding untreated DSSC (13.4 mA cm⁻²) using N719 and a 12 μm thick TiO₂ film at 100 mW cm⁻². The amount of N719 attached to the treated TiO₂ film was 21 % greater than that attached to the untreated TiO₂ film. Enhancement of the J_sc value by 15 % was attributed mostly to an intramolecular charge transfer from N719 attached to the Ge COOH Nps to the TiO₂ conduction band through the Ge COOH Nps.     

Synthesis and characterization of low‐band‐gap conjugated polymers containing phenothiazine and benzo‐2,1,3‐thia‐/seleno‐diazole

Two phenothiazine‐based conjugated polymers, poly(3, 7‐divinylene‐N‐octyl‐phenothiazine‐alt‐benzo‐2,1,3‐ thiadiazole) (PQS) and poly(3,7‐divinylene‐N‐octyl‐phenothiazine‐alt‐benzo‐2,1,3‐selenodiazole) (PQSe) were synthesized by Heck coupling reaction. The chemical structures of the two polymers were confirmed by ¹H‐NMR and Ft‐IR. They showed good solubility in some common organic solvents such as tetrahydrofuran (THF), chloroform. The weight‐average molecular weight (Mw) of the polymers determined by GPC in THF against polystyrene standards was 3.7 × 10³ for PQS and 1.9 × 10³ for PQSe, respectively. The temperatures of 5% weight loss (T₅) were 385.0°C for PQS and 324.0°C for PQSe, respectively, determined by TGA measurements under nitrogen ambience. UV–vis absorption spectra of the polymer films showed the absorption maxima at 537 nm for PQS and 539 nm for PQSe, with the full width at half maximum (FWHM) of 190 and 230 nm, respectively. The optical band gaps ( ) of the polymer films are 1.86 eV for PQS and 1.80 eV for PQSe, respectively. As the polymers have low‐band‐gap and broad absorption in the visible region, they may be used as potential light‐harvesting materials for photovoltaic devices (PVDs). Furthermore, photoluminescence (PL) spectra of the polymer solutions showed the emission maxima at 698 nm for PQS and 709 nm for PQSe, with FWHM of 152 nm and 167 nm, respectively, which revealed that these two polymers may be used as red and near infrared light‐emitting materials for polymeric light‐emitting diodes (PLEDs). Copyright © 2009 John Wiley & Sons, Ltd.     

Tris‐Heteroleptic Ruthenium–Dipyrrinate Chromophores in a Dye‐Sensitized Solar Cell

Two novel tris‐heteroleptic Ru–dipyrrinates were prepared and tested as sensitizers in the dye‐sensitized solar cell (DSSC). Under AM 1.5 sunlight, DSSCs employing these dyes achieved power conversion efficiencies (PCEs) of 3.4 and 2.2 %, substantially exceeding the value achieved previously with a bis‐heteroleptic dye (0.75 %). As shown by electrochemical measurements and DFT calculations, the improved PCEs stem from the synthetically tuned electronic structure, which affords more negative excited state redox potentials and favorable electron injection into the TiO₂ conduction band. Electron injection was quantified by nanosecond transient absorption spectroscopy, which revealed that the highest injection yield is achieved with the dye that acts as the strongest photoreductant.