The influence of noncovalent interactions in metal‐free organic dye molecules to augment the efficiency of dye sensitized solar cells: A computational study

The efficiency of dye sensitized solar cells (DSSCs) can be enhanced with achieving better planarity of metal‐free organic dye molecules and thinning of their aggregation on the semiconductor surface. We report that the subtle noncovalent N^…S interaction between the substituted phosphazene group and thiophene spacer unit in dye molecule which induces the desired planarity and avoid aggregation of such molecules on the TiO₂ surface using DFT calculations. DFT results show that phosphazene group increases the maximum absorption wavelength (λ_max), driving force for electrons injection (ΔG_injection), singlet excited state lifetime (τ), dipole moments (μ_normal), and number of electrons transferred from dye to TiO₂ surface (Δq), which are known to augment the efficiency of DSSCs. Further, the lower ΔG_regeneration value of phosphazene containing dyes (e.g., –.37 eV, dye 2 ) than the reported dyes (e.g., –.81 eV, dye 1 ) indicate the faster electron injection rate from the former dye to the semiconductor TiO₂. The role of phosphazene group to prevent the aggregation of dye molecules on the TiO₂ anatase surface was also examined with GGA‐PBE/DNP level of theory. The calculated results suggest that the dye molecules on 1 ‐(TiO₂)₃₈ and 2 ‐(TiO₂)₃₈ anatase clusters avoids the aggregation due to the steric congestion induced by phosphazene group. This work reports to accomplish dual properties with subtle noncovalent interactions in dye molecules to augment the efficiency in DSSCs.     

Photocurrent Enhancement of Dye‐Sensitized Solar Cells owing to Increased Dye‐Adsorption onto Silicon‐Nanoparticle‐Coated Titanium‐Dioxide Films

The inverse‐micellar preparation of Si nanoparticles (Nps) was improved by utilizing sodium naphthalide. The Si Nps were subsequently functionalized with 4‐vinylbenzoic acid for their attachment onto TiO₂ films of dye‐sensitized solar cells (DSSCs). The average diameter of the COOH‐functionalized Si (Si? COOH) Nps was 4.6(±1.7) nm. Depth profiling by secondary‐ion mass spectrometry revealed that the Si Nps were uniformly attached onto the TiO₂ films. The number of Ru^II dye molecules adsorbed onto a TiO₂ film that was treated with the Si? COOH Nps was 42 % higher than that on the untreated TiO₂ film. As a result, DSSCs that incorporated the Si? COOH Nps exhibited higher short‐circuit photocurrent density and an overall energy‐conversion efficiency than the untreated DSSCs by 22 % and 27 %, respectively. This enhanced performance, mostly owing to the intramolecular charge‐transfer to TiO₂ from the dye molecules that were anchored to the Si? COOH Nps, was confirmed by comparing the performance with two different Ru^II–bipyridine dyes (N719 and N749).     

Efficiency improvement of flexible dye-sensitized solar cells by introducing mesoporous TiO2 microsphere

Mesoporous TiO2microsphere(MTM)was synthesized via a simple solution route and then mixed with commercial TiO2(P25)to form highly homogeneous and stable TiO2colloid by simple hydrothermal treatment.The TiO2colloid was coated onto the plastic conductive substrate to prepare mesoporous TiO2film for flexible dye-sensitized solar cells(DSSCs)by low-temperature heat treatment.The influence of MTM content on the physicochemical properties of the flexible TiO2film was characterized by scanning electron microscope,transmission electron microscopy,X-ray diffraction,energy-dispersive X-ray spectrometer,N2adsorption-desorption isotherms,UV–vis absorption and diffuse reflectance spectra.It is revealed that with increasing the MTM content,the dye-loading capability of TiO2film and light-harvesting efficiency of flexible DSSCs are improved due to MTM having high surface area and acting as a light scattering center,respectively,resulting in the enhancement of photocurrent of flexible DSSCs.However,more and larger cracks having negative effect on the performances of flexible DSSCs are formed simultaneously.Under the optimal condition with MTM content of 20%,a flexible DSSC with overall light-to-electric energy conversion efficiency of 2.74%is achieved under a simulated solar light irradiation of 100 mW cm 2(AM 1.5),with 26%improvement in comparison with DSSCs based on P25 alone.     

Fabrication of highly efficient dye-sensitized solar cell and CO2 reduction photocatalyst using TiO2 nanoparticles prepared by spin coating-assisted sol–gel method

A sol?Cgel method was applied for fabrication of nanocrystalline anatase TiO₂ thin films on ITO glass substrates and followed by rapid thermal annealing for application as the work electrode for dye-sensitized solar cells (DSSC). TiO₂ nanoparticles were characterized by X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) and the absorption of dye on the TiO₂ electrode was shown by UV?Cvis spectroscopy. By controlling different parameters including numbers of coated layers, the gap between two electrodes, sensitization time, and light source power, TiO₂-based solar cells with high efficiency was achieved. The results show that a five time spin-coated TiO₂ electrode with applying sealant and sensitization time of 24?h in N3 dye under illumination of 100?W?cm^?2 tungsten lamp give the optimum power conversion efficiency (??) of 6.61%. The increases in thickness of TiO₂ films by increasing the numbers of coated layers can improve adsorption of the N3 dye through TiO₂ layers to increase the open-circuit voltage (V _oc). However, short-circuit photocurrents (J _sc) of DSSCs with a one-coated layer of TiO₂ films are smaller than those of DSSCs with five-coated layer of TiO₂ films. It could be due to the fact that the increased thickness of TiO₂ thin films also resulted in a decrease in the transmittance of TiO₂ thin films. Also, this electrode was employed to photoreduce CO₂ with H₂O under tungsten lamp as light source.     

Enhanced photovoltaic characterization and charge transport of TIO2 nanoparticles/nanotubes composite photoanode based on indigo carmine dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have established themselves as an alternative to conventional solar cells owing to their remarkably high power conversion efficiency, longtime stability and low-cost production. DSSCs composed of a dyed oxide semiconductor photoanode, a redox electrolyte and a counter electrode. In these devices, conversion efficiency is achieved by ultra-fast injection of an electron from a photo excited dye into the conduction band of metal oxide followed by subsequent dye regeneration and holes transportation to the counter electrode. The energy conversion efficiency of DSSC is to be dependent on the morphology and structure of the dye adsorbed metal oxide photoanode. Worldwide considerable efforts of DSSCs have been invested in morphology control of photoanode film, synthesis of stable optical sensitizers and improved ionic conductivity electrolytes. In the present investigation, a new composite nano structured photoanodes were prepared using TiO₂ nano tubes (TNTs) with TiO₂ nano particles (TNPs). TNPs were synthesized by sol–gel method and TNTs were prepared through an alkali hydrothermal transformation. Working photoanodes were prepared using five pastes of TNTs concentrations of 0, 10, 50, 90, and 100 % with TNPs. The DSSCs were fabricated using Indigo carmine dye as photo sensitizer and PMII (1-propyl-3-methylimmidazolium iodide) ionic liquid as electrolyte. The counter electrode was prepared using Copper sulfide. The structure and morphology of TNPs and TNTs were characterized by X-ray diffraction and electron microscopes (TEM and SEM). The photocurrent efficiency is measured using a solar simulator (100 mW/cm²). The prepared composite TNTs/TNPs photoanode could significantly improve the efficiency of dye-sensitized solar cells owing to its synergic effects, i.e. effective dye adsorption mainly originated from TiO₂ nanoparticles and rapid electron transport in one-dimensional TiO₂ nanotubes. The results of the present investigation suggested that the DSSC based on 10 % TNTs/TNPs showed better photovoltaic performance than cell made pure TiO₂ nanoparticles. The highest energy-conversion efficiency of 2.80 % is achieved by composite TNTs (10 %)/TNPs film, which is 68 % higher than that pure TNPs film and far larger than that formed by bare TNTs film (94 %). The charge transport and charge recombination behaviors of DSSCs were investigated by electrochemical impedance spectra and the results showed that composite TNTs/TNPs film-based cell possessed the lowest transfer resistances and the longest electron lifetime. Hence, it could be concluded that the composite TNTs/TNPs photoanodes facilitate the charge transport and enhancing the efficiencies of DSSCs.     

La3+’s Effect on the Surface (101) of Anatase for Methylene Blue Dye Removal,a DFT Study

Density functional theory (DFT) is a widely used method for studying matter at the quantum level. In this study, the surface (101) of TiO₂ (anatase phase) was considered to develop DFT calculations and explain the effect of lanthanum ion (La³⁺) on the electronic properties, adsorption capacity, and photocatalytic activity of this semiconductor. Due to the presence of the La³⁺ ion, the bandgap energy value of La/TiO₂ (2.98 eV) was lower than that obtained for TiO₂ (3.21 eV). TDOS analysis demonstrated the presence of hybrid levels in La/TiO₂ composed mainly of O2p and La5d orbitals. The chemical nature of the La-O bond was estimated from PDOS analysis, Bader charge analysis, and ELF function, resulting in a polar covalent type, due to the combination of covalent and ionic bonds. In general, the adsorption of the methylene blue (MB) molecule on the surface (101) of La/TiO₂ was energetically more favorable than on the surface (101) of TiO₂. The thermodynamic stability of doping TiO₂ with lanthanum was deduced from the negative heat-segmentation values obtained. The evidence from this theoretical study supports the experimental results reported in the literature and suggests that the semiconductor La/TiO₂ is a potential catalyst for applications that require sunlight.     

The enhanced photoelectric conversion efficiency of N3 sensitized MgTiO3 modified nanoporous TiO2 electrodes

The preparation of nanoporous TiO₂ electrodes modified with an MgTiO₃ layer and its application in dye-sensitized solar cells (DSSCs) were reported. The conduction band of MgTiO₃ stands higher than that of TiO₂, so the MgTiO₃ layer can be beneficial to the improvement of nanoporous TiO₂ electrodes. The as-prepared TiO₂/MgTiO₃ electrodes were characterized by XRD and the diffraction of its crystal plane (1 0 4) was detected, demonstrating the existence of MgTiO₃ phase on the surface of TiO₂. Compared with bare TiO₂ electrodes, MgTiO₃ modified TiO₂ electrodes presented more dye adsorption. Moreover an energy barrier formed as TiO₂ electrodes were modified with MgTiO₃ layer, which suppresses the charge recombination. As a result, the photoelectrochemical properties of the modified electrodes were improved and the overall energy conversion efficiency η was increased from 6.12% to 8.75% under the illumination of a white light of 100 mW/cm².     

An efficient method to prepare high-performance dye-sensitized photoelectrodes using ordered TiO<Subscript>2</Subscript> nanotube arrays and TiO<Subscript>2</Subscript> quantum dot blocking layers

High-performance dye-sensitized photoelectrodes using ordered TiO₂ nanotube arrays (TNTs) and TiO₂ quantum dot blocking layers are fabricated. The free-standing TNT membranes with perfect ordered morphology are prepared by three times of anodic oxidation on Ti foils. These TNT membranes can be easily transported to conductive glasses to fabricate front-side illuminated photoelectrodes. By changing anodic oxidation duration, the thickness of TNT membranes can be controlled, which shows significant influence on the UV-Vis reflectance and absorption abilities of TNT-based photoelectrodes and further influence photovoltaic performance of dye-sensitized solar cells (DSSCs). The highest power conversion efficiency (PCE) of DSSCs about 6.21 % can be obtained by using TNT membranes prepared with anodic oxidation of 3 h. For further improving photovoltaic performance of DSSCs, TiO₂ quantum dot (QDs) blocking layers are inserted between conductive glasses and TNT membranes in the photoelectrodes, which show remarkable effects. The highest PCE of DSSCs with this kind of blocking layers can increase to 8.43 %, producing 35.75 % enhancement compared with that of the counterparts without TiO₂ QD blocking layers.     

二氧化钛纳米晶溶胶内渗透电极对染料敏化太阳能电池的光伏性能的提高

以自制的过氧钛酸(PTA)水溶液为前驱体,用水热法制备了透明锐钛矿相二氧化钛溶胶.无需有机添加剂可得到直径小于7 nm的棒状二氧化钛纳米晶溶胶.通过将溶胶内渗透到染料敏化太阳能电池(DSSCs)的多孔二氧化钛电极后,消除了多孔电极内的大孔并改善了电极内纳米晶之间的连通性.用扫描电子显微镜(SEM)和光学轮廓仪对溶胶内渗透后的光阳极进行了表征.结果表明:小颗粒棒状二氧化钛纳米晶附着在多孔的二氧化钛表面,填充了电极由于烧结产生的大孔,并在多孔的二氧化钛内部形成了有利于电子传输的网络结构.与未经处理的多孔电极相比,改性后的光阳极组装成染料敏化太阳能电池后光电转化效率提高了64%.     

Performance of dye-sensitized solar cells based on various sensitizers applied on TiO2-Nb2O5 core/shell photoanode structure

The present investigation described the performance of dye-sensitized solar cells (DSSCs) based on various sensitizers applied on TiO₂-Nb₂O₅ core/shell photoanode film. The novel photoanodes were prepared using composite of TiO₂ nanoparticles (TNPs) and TiO₂ nanorods (TNRs) as core (TNPRs) layer with Nb₂O₅ shell coating. As well, tantalum pentoxide (Ta₂O₅), a blocking layer applied over the core/shell film. The DSSCs were fabricated based on various sensitizers namely zinc phthalocyanine, indoline, indigo carmine, zinc porphyrin, N719, coumarin NKX-2700, polymer dye, quantum dots (QDs), perylene and squaraine. The I–V characteristics of the DSSCs, photocurrent density (Jsc), open-circuit voltage (Voc), fill factor (FF), and photoconversion efficiency (PCE) were determined under illumination of AM 1.5 G. Electrochemical impedance spectroscopy (EIS) analysis is carried out to study the charge transport and life-time of charge carriers at photoanode/dye/electrolyte interface of the DSSCs. The I–V and EIS results explicated that the core/shell with blocking layers were able to alleviate the electron transport and suppressed charge recombination at photoanode/dye/electrolyte interface of the DSSCs. Concerning the sensitizers, PCE of the DSSCs exemplify the order N719 > zinc porphyrin > coumarin NKX-2700 > indoline > squaraine > QDs > zinc phthalocyanine > perylene > polymer dye > indigo carmine dye. The results of the present work demonstrated that among the sensitizers studied, N719 showed the highest PCE and fill factor. Besides, the metal-free organic sensitizers (coumarin NKX-2700 and indoline) exhibited comparable PCE as compared to N719.     

Photoanode Based on Chain‐Shaped Anatase TiO2 Nanorods for High‐Efficiency Dye‐Sensitized Solar Cells

Anatase TiO₂ nanorods with large specific surface areas and high crystallinity have been synthesized by surfactant‐free hydrothermal treatment of water‐soluble peroxotitanium acid (PTA). X‐ray diffraction and TEM analysis showed that all TiO₂ nanorods derived from PTA in different hydrothermal processes were in the anatase phase, and high aspect ratio TiO₂ nanorods with chain‐shaped structures were formed at 150 °C for 24 h by oriented growth. The nanorods were fabricated as photoanodes for high‐efficiency dye‐sensitized solar cells (DSSCs). DSSCs fabricated from the chain‐shaped TiO₂ nanorods gave a highest short‐circuit current density of 14.8 mA cm^?2 and a maximum energy conversion efficiency of 7.28 %, as a result of the presence of far fewer surface defects and grain boundaries than are present in commercial P25 TiO₂ nanoparticles. Electrochemical impedance spectroscopy also confirmed that DSSCs based on the TiO₂ nanorods have enhanced electron transport properties and a long electron lifetime.     

CdSe量子点敏化纳米二氧化钛太阳电池的电化学交流阻抗谱

量子点敏化纳米TiO2太阳电池(QDSSCs)具有诱人的发展前景,但是与传统的染料敏化太阳电池(DSSCs)相比,其目前的光电转换效率还非常低(仅为3%左右).为了寻找QDSSCs光电转换效率低的原因,本文主要采用外加偏压下的交流阻抗谱技术对通常以S2-/S-x离子对为电解质的CdSe胶体量子点敏化纳米TiO2电极的准...     

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.     

Effects of electron beam irradiation on the photoelectrochemical properties of TiO2 film for DSSCs

TiO₂ has been widely utilized for various industrial applications such as photochemical cells, photocatalysts, and electrochromic devices. The crystallinity and morphology of TiO₂ films play a significant role in determining the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, the preparation of nanostructured TiO₂ films by electron beam irradiation and their characterization were investigated for the application of DSSCs. TiO₂ films were exposed to 20–100 kGy of electron beam irradiation using 1.14 MeV energy acceleration with a 7.46 mA beam current and 10 kGy/pass dose rates. These samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) analysis. After irradiation, each TiO₂ film was tested as a DSSC. At low doses of electron beam irradiation (20 kGy), the energy conversion efficiency of the film was approximately 4.0% under illumination of simulated sunlight with AM 1.5 G (100 mW/cm²). We found that electron beam irradiation resulted in surface modification of the TiO₂ films, which could explain the observed increase in the conversion efficiency in irradiated versus non-irradiated films.     

Surface modification of TiO2 nanoparticles with AHAPS aminosilane: distinction between physisorption and chemisorption

This paper addresses the surface modification of TiO₂ nanoparticles with n-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS) using various initial aminosilane concentrations. The main objective of this article is to show experimentally the importance of the physisorption during the grafting process. The distinction between chemisorbed and physisorbed aminosilane molecules on TiO₂ is thoroughly analyzed. The surface of bare and modified TiO₂ particles has been characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to gain a better understanding of the adsorption mechanism of AHAPS on TiO₂. Quantitative information on surface energy of TiO₂, in terms of adsorption energy sites and heterogeneity, has been investigated by quasi-equilibrium low-pressure adsorption technique using nitrogen and argon as probe molecules. The FTIR and XPS data are combined to estimate and discuss the chemisorbed and physisorbed contribution. The results demonstrate that both physisorption and chemisorption occurs but they display a different behavior. The physisorbed amounts are much higher than the chemisorbed amounts. This shows that the main part of the adsorbed layer is composed of physisorbed molecules. The physisorbed uptake depends highly on the AHAPS concentration while the chemisorbed amount remains constant. Quasi-equilibrium Ar derivative adsorption isotherms reveal that the AHAPS molecules are mostly located on the {101} and {001} faces of titania and that the two faces display the same reactivity toward AHAPS sorption. Nitrogen adsorption experiments show that the sorption takes place on the three polar surface sites of high energy. The molecules are chemisorbed onto the site displaying the highest energy while they are physisorbed on the two lower energy sites.     

Engineering large-scaled electrochromic semiconductor films as reproductive SERS substrates for operando investigation at the solid/liquid interfaces

Although surface-enhanced Raman spectroscopy (SERS) has been applied for gathering fingerprint information, even in single molecule analysis, the decayed Raman signals in aqueous solutions largely obstruct the on-site insight reaction process. In this study, large-scaled semiconductor films with multi-walled (TiO₂/WO₃/TiO₂) nanopore distribution are fabricated by combining electrochemical anodization and sputtering technique, and then employed as the SERS substrates for detection of molecules at the solid/liquid interfaces. Given the remarkably improved electrochromic property of the multi-walled film, such SERS substrates were endowed with tunable oxygen vacancy (V_O) density and distribution via simply applying electrochemical bias voltage, which enabled one to achieve an enhanced charge transfer efficiency and thus a remarkably increased Raman signal even in solution. The V_O-rich SERS substrate is highly repeatable, thus providing a reliable platform for in-situ monitoring of the target molecules or intermediates at the solid/liquid interfaces.     

Solar Driven Photocatalytic Activity of Porphyrin Sensitized TiO2: Experimental and Computational Studies

The absence of a secure long-term sustainable energy supply is recognized as a major worldwide technological challenge. The generation of H₂ through photocatalysis is an environmentally friendly alternative that can help solve the energy problem. Thus, the development of semiconductor materials that can absorb solar light is an attractive approach. TiO₂ has a wide bandgap that suffers from no activity in the visible spectrum, limiting its use of solar radiation. In this research, the semiconductor absorption profile was extended into the visible region of the solar spectrum by preparing porphyrin-TiO₂ (P-TiO₂) composites of meso-tetra(4-bromophenyl)porphyrin (PP1) and meso-tetra(5-bromo-2-thienyl)porphyrin (PP2) and their In(III), Zn(II) and Ga(III) metal complexes. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were performed on the porphyrins to gain insight into their electron injection capability. The results demonstrate that P-TiO₂ systems merit further in-depth study for applications that require efficient photocatalytic H₂ generation.     

N-doped TiO<Subscript>2</Subscript> applied in low-temperature-based dye-sensitized solar cells

With urea as nitrogen source, N-doped TiO₂ powders were synthesized and fabricated for low-temperature dye-sensitized solar cells (DSSCs) by the method of doctor-blade, and the highest temperature of the whole process was 120 °C. SEM, TEM, XRD, DRS, and XPS were used to analyze the microstructure of the N-doped TiO₂ powders. EIS, Bode plot, UV–Vis and I–V were employed to measure the photovoltaic performance of the DSSCs. The maximum photoelectric conversion efficiency (η) was 5.18 % when the amount of the doped nitrogen was 4 %, and, when compared with the η of 4.22 % for pure TiO₂, the short circuit current was increased by 22.2 % and the efficiency was increased by 22.7 %. It has been shown that the doped nitrogen could effectively suppress TiO₂ crystal phase transition from anatase to rutile, and decrease the size of particles. Therefore, the increased photoelectric conversion efficiency of the N-doped TiO₂-based DSSC was ascribed to the more suitable crystal phase, sizes and inner structure.     

Adsorption of CH3 COOH on TiO2: IR and theoretical investigations

Adsorption of organic molecules on TiO₂ surfaces is widely used in a number of technological applications, from heterogeneous catalysis, in particular photodegradation of organic pollutants, to dye-sensitized solar cells (DSSCs), where in most cases the dye molecules are grafted to the anatase TiO₂ surface through a carboxylic group. In particular, organic/TiO₂ systems can be of relevant importance in the modeling of electronic devices, in which the molecular layer is able to finely tune the electric properties, as well as of highly efficient heterogeneous catalysts. A key step is the understanding of the nature of the carbon-oxygen-titanium bonds on such surfaces, which is the specific aim of our combined IR and ab initio study of the adsorption of CH₃COOH on TiO₂. The experimental determination of the CH₃COOH frequency shifts due to the absorption on the P25 (Degussa) TiO₂ surface was performed by means of a step-wise procedure, consisting of a preliminary outgassing at 600°C of TiO₂, in order to have a high dehydroxilation degree of the surface, followed by IR measurements at increasing CH₃COOH pressure and subsequent desorption. Frequency calculations to be compared with experimental results were performed within a cluster approach using GAUSSIAN03 package. In order to make such calculations feasible, we decided to use an ONIOM approach where the model system, i.e., the small portion corresponding to CH₃COOH plus the surface atoms, is treated at DFT level while the real system, comprising the bulk atoms, at MSINDO level. Once properly tested the ONIOM approach to characterize the interaction of TiO₂ with CH₃COOH, we computed the vibrational frequencies and compared them with the results of the IR experiments, providing some insight for the interpretation of the experimental complex vibrational pattern.     

Dipolar Compounds Containing Fluorene and a Heteroaromatic Ring as the Conjugating Bridge for High‐Performance Dye‐Sensitized Solar Cells

A novel series of dipolar organic dyes containing diarylamine as the electron donor, 2‐cyanoacrylic acid as the electron acceptor, and fluorene and a heteroaromatic ring as the conjugating bridge have been developed and characterized. These metal‐free dyes exhibited very high molar extinction coefficients in the electronic absorption spectra and have been successfully fabricated as efficient nanocrystalline TiO₂ dye‐sensitized solar cells (DSSCs). The solar‐energy‐to‐electricity conversion efficiencies of DSSCs ranged from 4.92 to 6.88 %, which reached 68–96 % of a standard device of N719 fabricated and measured under the same conditions. With a TiO₂ film thickness of 6 μm, DSSCs based on these dyes had photocurrents surpassing that of the N719‐based device. DFT computation results on these dyes also provide detailed structural information in connection with their high cell performance.