Dye‐Sensitized Solar Cells Based on (Donor‐π‐Acceptor)2 Dyes With Dithiafulvalene as the Donor

Dipolar metal‐free sensitizers (D‐π‐A; D=donor, π=conjugated bridge, A=acceptor) consisting of a dithiafulvalene (DTF) unit as the electron donor, a benzene, thiophene, or fluorene moiety as the conjugated spacer, and 2‐cyanoacrylic acid as the electron acceptor have been synthesized. Dimeric congeners of these dyes, (D‐π‐A)₂, were also synthesized through iodine‐induced dimerization of an appropriate DTF‐containing segment. Dye‐sensitized solar cells (DSSCs) with the new dyes as the sensitizers have cell efficiencies that range from 2.11 to 5.24 %. In addition to better light harvesting, more effective suppression of the dark current than the D‐π‐A dyes is possible with the (D‐π‐A)₂ dyes.     

Constructing Organic D–A–π‐A‐Featured Sensitizers with a Quinoxaline Unit for High‐Efficiency Solar Cells: The Effect of an Auxiliary Acceptor on the Absorption and the Energy Level Alignment

Four organic D–A –π‐A‐featured sensitizers (TQ1, TQ2, IQ1, and IQ2) have been studied for high‐efficiency dye‐sensitized solar cells (DSSCs). We employed an indoline or a triphenylamine unit as the donor, cyanoacetic acid as the acceptor/anchor, and a thiophene moiety as the conjugation bridge. Additionally, an electron‐withdrawing quinoxaline unit was incorporated between the donor and the π‐conjugation unit. These sensitizers show an additional absorption band covering the broad visible range in solution. The contribution from the incorporated quinoxaline was investigated theoretically by using DFT and time‐dependent DFT. The incorporated low‐band‐gap quinoxaline unit as an auxiliary acceptor has several merits, such as decreasing the band gap, optimizing the energy levels, and realizing a facile structural modification on several positions in the quinoxaline unit. As demonstrated, the observed additional absorption band is favorable to the photon‐to‐electron conversion because it corresponds to the efficient electron transitions to the LUMO orbital. Electrochemical impedance spectroscopy (EIS) Bode plots reveal that the replacement of a methoxy group with an octyloxy group can increase the injection electron lifetime by a factor of 2.4. IQ2 and TQ2 can perform well without any co‐adsorbent, successfully suppress the charge recombination from TiO₂ conduction band to I₃^? in the electrolyte, and enhance the electron lifetime, resulting in a decreased dark current and enhanced open circuit voltage (V_oc) values. By using a liquid electrolyte, DSSCs based on dye IQ2 exhibited a broad incident photon‐to‐current conversion efficiency (IPCE) action spectrum and high efficiency (η=8.50 %) with a short circuit current density (J_sc) of 15.65 mA cm^?2, a V_oc value of 776 mV, a fill factor (FF) of 0.70 under AM 1.5 illumination (100 mW cm^?2). Moreover, the overall efficiency remained at 97 % of the initial value after 1000 h of visible‐light soaking.     

Benzimidazole‐indole‐chalcone connected methacrylate‐based side chain D‐π‐A polymer and its application in organic photovoltaics

Herein, we report four metal‐free organic polymethacrylates (In‐In‐BzI)PMA , (Ac‐In‐BzI)PMA , (TPA‐In‐BzI)PMA , and (Py‐In‐BzI)PMA with pendant chromophores donor‐π‐conjugated‐acceptor (D‐π‐A) molecular framework as photosensitizers for dye‐sensitized solar cells (DSSCs). In which the donor‐acceptor units are attached by an indole‐chalcone extending side chain to inhibit back electron transfer and charge recombination; the π‐linker component contains varied chalcone‐based substituents to enhance the sunlight‐harvesting ability of the solar device. Photon‐current cells based on the DSSC format were fabricated using the polymers as sensitizers. The DSSC device assembled using (TPA‐In‐BzI)PMA exhibits a considerably better IPCE peak and J–V response, with an overall power conversion efficiency of 3.70% under the illumination of AM 1.5G (100 mW cm^–2). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 997–1007     

Structure–Performance Correlations of Organic Dyes with an Electron‐Deficient Diphenylquinoxaline Moiety for Dye‐Sensitized Solar Cells

The high performances of dye‐sensitized solar cells (DSSCs) based on seven new dyes are disclosed. Herein, the synthesis and electrochemical and photophysical properties of a series of intentionally designed dipolar organic dyes and their application in DSSCs are reported. The molecular structures of the seven organic dyes are composed of a triphenylamine group as an electron donor, a cyanoacrylic acid as an electron acceptor, and an electron‐deficient diphenylquinoxaline moiety integrated in the π‐conjugated spacer between the electron donor and acceptor moieties. The DSSCs based on the dye DJ104 gave the best overall cell performance of 8.06 %; the efficiency of the DSSC based on the standard N719 dye under the same experimental conditions was 8.82 %. The spectral coverage of incident photon‐to‐electron conversion efficiencies extends to the onset at the near‐infrared region due to strong internal charge‐transfer transition as well as the effect of electron‐deficient diphenylquinoxaline to lower the energy gap in these organic dyes. A combined tetraphenyl segment as a hydrophobic barrier in these organic dyes effectively slows down the charge recombination from TiO₂ to the electrolyte and boosts the photovoltage, comparable to their Ru^II counterparts. Detailed spectroscopic studies have revealed the dye structure–cell performance correlations, to allow future design of efficient light‐harvesting organic dyes.     

Dye-sensitized solar cells based on donor-π-acceptor fluorescent dyes with a pyridine ring as an electron-withdrawing-injecting anchoring group

A new‐type of donor–acceptor π‐conjugated (D‐π‐A) fluorescent dyes NI3 – NI8 with a pyridine ring as electron‐withdrawing‐injecting anchoring group have been developed and their photovoltaic performances in dye‐sensitized solar cells (DSSCs) are investigated. The short‐circuit photocurrent densities and solar energy‐to‐electricity conversion yields of DSSCs based on NI3 – NI8 are greater than those for the conventional D‐π‐A dye sensitizers NI1 and NI2 with a carboxyl group as the electron‐withdrawing anchoring group. The IR spectra of NI3 – NI8 adsorbed on TiO₂ indicate the formation of coordinate bonds between the pyridine ring of dyes NI3 – NI8 and the Lewis acid sites (exposed Tiⁿ⁺ cations) of the TiO₂ surface. This work demonstrates that the pyridine rings of D‐π‐A dye sensitizers that form a coordinate bond with the Lewis acid site of a TiO₂ surface are promising candidates as not only electron‐withdrawing anchoring group but also electron‐injecting group, rather than the carboxyl groups of the conventional D‐π‐A dye sensitizers that form an ester linkage with the Brønsted acid sites of the TiO₂ surface.     

Synthesis and Characterization of Donor–π‐Acceptor‐Based Porphyrin Sensitizers: Potential Application of Dye‐Sensitized Solar Cells

New porphyrin sensitizers based on donor–π‐acceptor (D‐π‐A) approach have been designed, synthesized, characterized by various spectroscopic techniques and their photovoltaic properties explored. N,N′‐Diphenylamine acts as donor, the porphyrin is the π‐spacer, and either carboxylic acid or cyanoacryclic acid acts as acceptor. All compounds were characterized by using ¹H NMR spectroscopy, ESI‐MS, UV–visible emission spectroscopies as well as electrochemical methods. The presence of aromatic groups between porphyrin π‐plane and acceptor group push the absorption of both Soret and Q‐bands of porphyrin towards the red region. The electrochemical properties suggests that LUMO of these sensitizers above the TiO₂ conduction band. Finally, the device was fabricated using liquid redox electrolyte (I^?/I₃^?) and its efficiency was compared with that of a leading sensitizer.     

Novel Thiazolo[5,4‐d]thiazole‐Based Organic Dyes for Quasi‐Solid‐State Dye‐Sensitized Solar Cells

A series of novel metal‐free organic dyes containing the thiazolo[5,4‐d]thiazole moiety were designed and synthesized for quasi‐solid‐state dye‐sensitized solar cells (DSSCs). Different alkoxy chains were introduced into the electron donor part of the dye molecules for comparison. The optical, electrochemical, and photovoltaic properties for all sensitizers were systematically investigated. It was found that the sensitizers with the different alkoxy groups have similar photophysical and electrochemical properties, such as absorbance and energy levels, owing to their close chemical structures. However, the quasi‐solid‐state DSSCs based on the resulting sensitizers exhibit different performance parameters. The quasi‐solid‐state DSSC based on sensitizer FNE74 with two octyloxy chains possessed the highest solar energy conversion efficiency of 5.10 % under standard AM 1.5G sunlight illumination without the use of coadsorbant agents.     

Phenanthrene‐Fused‐Quinoxaline as a Key Building Block for Highly Efficient and Stable Sensitizers in Copper‐Electrolyte‐Based Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSSCs) based on Cu^II/I bipyridyl or phenanthroline complexes as redox shuttles have achieved very high open‐circuit voltages (V_OC, more than 1 V). However, their short‐circuit photocurrent density (J_SC) has remained modest. Increasing the J_SC is expected to extend the spectral response of sensitizers to the red or NIR region while maintaining efficient electron injection in the mesoscopic TiO₂ film and fast regeneration by the Cu^I complex. Herein, we report two new D‐A‐π‐A‐featured sensitizers termed HY63 and HY64 , which employ benzothiadiazole (BT) or phenanthrene‐fused‐quinoxaline (PFQ), respectively, as the auxiliary electron‐withdrawing acceptor moiety. Despite their very similar energy levels and absorption onsets, HY64 ‐based DSSCs outperform their HY63 counterparts, achieving a power conversion efficiency (PCE) of 12.5 %. PFQ is superior to BT in reducing charge recombination resulting in the near‐quantitative collection of photogenerated charge carriers.     

Photophysical and Electrochemical Properties,and Molecular Structures of Organic Dyes for Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSSCs) based on organic dyes adsorbed on oxide semiconductor electrodes, such as TiO₂, ZnO, or NiO, which have emerged as a new generation of sustainable photovoltaic devices, have attracted much attention from chemists, physicists, and engineers because of enormous scientific interest in not only their construction and operational principles, but also in their high incident‐solar‐light‐to‐electricity conversion efficiency and low cost of production. To develop high‐performance DSSCs, it is important to create efficient organic dye sensitizers, which should be optimized for the photophysical and electrochemical properties of the dyes themselves, with molecular structures that provide good light‐harvesting features, good electron communication between the dye and semiconductor electrode and between the dye and electrolyte, and to control the molecular orientation and arrangement of the dyes on a semiconductor surface. The aim of this Review is not to make a list of a number of organic dye sensitizers developed so far, but to provide a new direction in the epoch‐making molecular design of organic dyes for high photovoltaic performance and long‐term stability of DSSCs, based on the accumulated knowledge of their photophysical and electrochemical properties, and molecular structures of the organic dye sensitizers developed so far.     

Synthesis and Characterization of Organic Dyes with Various Electron‐Accepting Substituents for p‐Type Dye‐Sensitized Solar Cells

Four new donor‐π‐acceptor dyes differing in their acceptor group have been synthesized and employed as model systems to study the influence of the acceptor groups on the photophysical properties and in NiO‐based p‐type dye‐sensitized solar cells. UV/Vis absorption spectra showed a broad range of absorption coverage with maxima between 331 and 653 nm. Redox potentials as well as HOMO and LUMO energies of the dyes were determined from cyclic voltammetry measurements and evaluated concerning their potential use as sensitizers in p‐type dye‐sensitized solar cells (p‐DSCs). Quantum‐chemical density functional theory calculations gave further insight into the frontier orbital distributions, which are relevant for the electronic processes in p‐DSCs. In p‐DSCs using an iodide/triiodide‐based electrolyte, the polycyclic 9,10‐dicyano‐acenaphtho[1,2‐b]quinoxaline (DCANQ) acceptor‐containing dye gave the highest power conversion efficiency of 0.08 %, which is comparable to that obtained with the perylenemonoimide (PMI)‐containing dye. Interestingly, devices containing the DCANQ‐based dye achieve a higher V_OC of 163 mV compared to 158 mV for the PMI‐containing dye. The result was further confirmed by impedance spectroscopic analysis showing higher recombination resistance and thus a lower recombination rate for devices containing the DCANQ dye than for PMI dye‐based devices. However, the use of the strong electron‐accepting tricyanofurane (TCF) group played a negative role in the device performance, yielding an efficiency of only 0.01 % due to a low‐lying LUMO energy level, thus resulting in an insufficient driving force for efficient dye regeneration. The results demonstrate that a careful molecular design with a proper choice of the acceptor unit is essential for development of sensitizers for p‐DSCs.     

New Dual Donor–Acceptor (2D‐π‐2A) Porphyrin Sensitizers for Stable and Cost‐Effective Dye‐Sensitized Solar Cells

A series of porphyrin sensitizers that featured two electron‐donating groups and dual anchoring groups that were connected through a porphine π‐bridging unit have been synthesized and successfully applied in dye‐sensitized solar cells (DSSCs). The presence of electron‐donating groups had a significant influence on their spectroscopic, electrochemical, and photovoltaic properties. Overall, the dual anchoring groups gave tunable electronic properties and stronger attachment to TiO₂. These new dyes were readily synthesized in a minimum number of steps in gram‐scale quantities. Optical and electrochemical data confirmed the advantages of these dyes for use as sensitizers in DSSCs. Porphyrins with electron‐donating amino moieties provided improved charge separation and better charge‐injection efficiencies for the studied dual‐push–pull dyes. Attenuated total reflectance–Fourier‐transform infrared (ATR‐FTIR) and X‐ray photoelectron spectroscopy of the porphyrin dyes on TiO₂ suggest that both p‐carboxyphenyl groups are attached onto TiO₂, thereby resulting in strong attachment. Among these dyes, cis-Zn2BC2A , with two electron‐donating 3,6‐ditertbutyl‐phenyl‐carbazole groups and dual‐anchoring p‐carboxyphenyl groups, showed the highest efficiency of 4.07 %, with J_SC=9.81 mA cm^?2, V_OC=0.63 V, and FF=66 %. Our results also indicated a better photostability of the studied dual‐anchored sensitizers compared to their mono‐anchored analogues under identical conditions. These results provide insight into the developments of a new generation of high‐efficiency and thermally stable porphyrin sensitizers.     

The Structure‐property Relationships of D‐π‐A BODIPY Dyes for Dye‐sensitized Solar Cells

BODIPY dyes have attracted considerable attention as potential photosensitizers in dye‐sensitized solar cells (DSSCs) owing to their excellent optical properties and facile structural modification. This account focuses on recent advances in the molecular design of D‐π‐A BODIPY dyes for applications in DSSCs. Special attention has been paid to the structure‐property relationships of D‐π‐A BODIPY dyes for DSSCs. The developmental process in the modified position at the BODIPY core with a donor/acceptor is described. The devices based on 2,6‐modified BODIPY dyes exhibit better photovoltaic performance over other modified BODIPY dyes. Meanwhile, the research reveals the correlation of molecular structures (various donor chromophores, extended units, molecular frameworks, and long alkyl groups) with their photophysical and electrochemical properties and relates it to their performance in DSSCs. The structure‐property relationships give valuable information and guidelines for designing new D‐π‐A BODIPY dyes for DSSCs.

     

Molecular Design of D‐π‐A Type II Organic Sensitizers for Dye Sensitized Solar Cells

Four new type II organic dyes with D‐π‐A structure (donor‐π‐conjugated‐acceptor) and two typical type II sensitizers based on catechol as reference dyes are synthesized and applied in dye sensitized solar cells (DSCs). The four dyes can be adsorbed on TiO₂ through hydroxyl group directly. Electron injection can occur not only through the anchoring group (hydroxyl group) but also through the electron‐withdrawing group (? CN) located close to the semiconductor surface. Experimental results show that the type II sensitizers with a D‐π‐A system obviously outperform the typical type II sensitizers providing much higher conversion efficiency due to the strong electronic push‐pull effect. Among these dyes, LS223 gives the best solar energy conversion efficiency of 3.6%, with J_sc=7.3 mA·cm^?2, V_oc=0.69 V, FF=0.71, the maximum IPCE value reaches 74.9%.     

High‐Performance Dipolar Organic Dyes with an Electron‐Deficient Diphenylquinoxaline Moiety in the π‐Conjugation Framework for Dye‐Sensitized Solar Cells

We report here the synthesis and electrochemical and photophysical properties of a series of easily prepared dipolar organic dyes and their application in dye‐sensitized solar cells (DSSCs). For the six organic dyes, the molecular structures comprised a triphenylamine group as an electron donor, a cyanoacrylic acid as an electron acceptor, and an electron‐deficient diphenylquinoxaline moiety integrated in the π‐conjugated spacer between the electron donor and acceptor moieties. The incorporation of the electron‐deficient diphenylquinoxaline moiety effectively reduces the energy gap of the dyes and broadly extends the spectral coverage. DSSCs based on dye 6 produced the best overall cell performance of 7.35 %, which translates to approximately 79 % of the intrinsic efficiency of the DSSCs based on the standard N719 dye under identical experimental conditions. The high performance of DSSCs based on dye 6 among the six dyes explored is attributed to the combined effects of high dye loading on a TiO₂ surface, rapid dye regeneration, and effective retardation of charge recombination.     

Organic Dyes Containing Pyrenylamine‐Based Cascade Donor Systems with Different Aromatic π Linkers for Dye‐Sensitized Solar Cells: Optical,Electrochemical, and Device Characteristics

New organic dyes containing pyrenylamine donors in a cascade arrangement and cyanoacrylic acid acceptors have been synthesized and characterized by optical, electrochemical, and theoretical studies. The dyes inherit a D ‐π¹‐D ‐π²‐A (D=donor, A=acceptor) molecular architecture where the π linkers π¹ are changed from phenyl to biphenyl and fluorene, whereas the π linker π² that connects the donor fragment with the acceptor is a phenyl unit. The conjugation pathway linking the two donor segments has been found to play a major role in the optical and electrochemical properties. Shorter π linkers such as phenyl groups facilitate the donor–acceptor interaction while the nonplanar biphenyl spacer decreases the electronic communication between the donors and enhances the oxidation propensity of the corresponding dye. All the dyes display an intense longer wavelength electronic transition,which is attributable to the amine‐to‐cyanoacrylic acid charge transfer. The extinction coefficient of this peak grows dramatically on increasing the conjugation pathway length between the two donor segments. The dyes were used as sensitizers in nanocrystalline TiO₂‐based dye‐sensitized solar cells (DSSCs) and the cascade donor system contributed to the enhancement in the device efficiency due to favorable absorption and redox properties.     

Regioisomeric Effects on the Electronic Features of Indenothiophene‐Bridged D–π‐A′–A DSSC Sensitizers

Two D–π‐A′–A regioisomers (A‐IDT‐D and D‐IDT‐A) featuring 4,4′‐di‐p‐tolyl‐4 H‐indeno[1,2‐b]‐thiophene as a π linker (π) between the diarylamino donor (D) and the pyrimidine–cyanoacrylic acid acceptor (A′–A) have been successfully synthesized and characterized as efficient sensitizers for the dye‐sensitized solar cells (DSSCs). The different arrangements of the D and A′–A blocks on the unsymmetrical indenothiophene (IDT) core render the dipole of IDT being along (A‐IDT‐D) or opposite (D‐IDT‐A) to the direction of intramolecular (donor‐to‐acceptor) charge transfer, and thus induce variations in the physical properties. The experimental observations correlated well with the theoretical analyses, clearly revealing the trade‐off between the molar extinction coefficient (ε) and the S₀→S₁ transition energy. As a result, a superior ε value was observed for D‐IDT‐A, whereas a bathochromic shift in the absorption occurred in A‐IDT‐D. The larger ε value of D‐IDT‐A together with its more favorable energy level relative to TiO₂ led to a higher power conversion efficiency of 7.41 % for the D‐IDT‐A‐based DSSC, retaining approximately 95 % of the N719‐based DSSC efficiency. This work manifests the clear structure–property relationship for the case of donor and acceptor components being connected by an unsymmetrical π linker and provides insights for molecular engineering of organic sensitizers.     

Novel Metal Complexes Unit of Phenanthroline Derivative for Being Used as Auxiliary Electron Acceptor in Dye Sensitizer Molecules

Donor-acceptor-π bridge-acceptor (D−A−π−A) motif dyes are promising dye sensitizers in dye-sensitized solar cells (DSSCs). In this study, to strengthen with-drawing electron force of the auxiliary electron acceptors(A) in D−A−π−A motif dye sensitizers, the metal complexes unit is be used as auxiliary electron acceptor(A) instead of organic electron-withdrawing monomer. The four polymeric metal complexes were designed, synthesized, and characterized, which used metal complexes of phenanthroline derivatives as auxiliary acceptors (A), benzodithiophene-dithiophene derivatives (BDTT) as donors (D), and 8-hydroxyquinoline derivatives as π-bridges and acceptors of the dye sensitizers, and have been used for dye sensitizers. Under AM 1.5 G (100 mW cm⁻²), the photovoltaic test results indicated that the short-circuit photocurrent density (J_sc) of the DSSCs based four polymeric metal complexes are 11.26, 13.68, 14.42 and 15.57 mA cm⁻² and power conversion efficiency (PCE) are 5.96 %, 7.83 %, 8.07 %, 9.28 % respectively. Both J_sc and PCE value of the four polymeric metal complexes increased in order. This may be due to the fact that larger radius of metal ion under the same change number can enhance the coordination bond and cause stronger electron-withdrawing ability of auxiliary acceptor and stronger charge-transfer ability between the donor and the acceptor, which results in higher J_sc and higher PCE of the polymeric complex dye sensitizer.     

1‐Alkyl‐1H‐imidazole‐Based Dipolar Organic Compounds for Dye‐Sensitized Solar Cells

A series of donor–π–acceptor‐type organic dyes based on 1‐alkyl‐1H‐imidazole spacers 1 , 2 , 3 , 4 , 5 have been developed and characterized. The two electron donors are at positions 4 and 5 of the imidazole, while the electron‐accepting cyanoacrylic acid is incorporated at position 2 by a spacer‐containing heteroaromatic rings, such as thiophene and thiazole. Detailed investigation on the relationship between the structure, spectral and electrochemical properties, and performance of DSSC is described here. Dye‐sensitized solar cells (DSSCs) using dyes as the sensitizers exhibit good efficiencies, ranging from 3.06 to 6.35 %, which reached 42–87 % with respect to that of N719‐based device (7.33 %) fabricated and measured under similar conditions. Time‐dependent density functional theory (TDDFT) calculations have been performed on the dyes, and the results show that both electron donors can contribute to electron injection upon photo‐excitation, either directly or indirectly by internal conversion to the lowest excited state.     

Dye‐Sensitized Solar Cells Based on a Donor–Acceptor System with a Pyridine Cation as an Electron‐Withdrawing Anchoring Group

New hemicyanine dyes ( CM101 , CM102 , CM103 , and CM104 ) in which tetrahydroquinoline derivatives are used as electron donors and N‐(carboxymethyl)‐pyridinium is used as an electron acceptor and anchoring group were designed and synthesized for dye‐sensitized solar cells (DSSCs). Compared with corresponding dyes that have cyanoacetic acid as the acceptor, N‐(carboxymethyl)‐pyridinium has a stronger electron‐withdrawing ability, which causes the absorption maximum of dyes to be redshifted. The photovoltaic performance of the DSSCs based on dyes CM101 – CM104 markedly depends on the molecular structures of the dyes in terms of the n‐hexyl chains and methoxyl. The device sensitized by dye CM104 achieved the best conversion efficiency of 7.0 % (J_sc=13.4 mA cm^?2, V_oc=704 mV, FF=74.8 %) under AM 1.5 irradiation (100 mW cm^?2). In contrast, the device sensitized by reference dye CMR104 with the same donor but the cyanoacetic acid as the acceptor gave an efficiency of 3.4 % (J_sc=6.2 mA cm^?2, V_oc=730 mV, FF=74.8 %). Under the same conditions, the cell fabricated with N719 sensitized porous TiO₂ exhibited an efficiency of 7.9 % (J_sc=15.4 mA cm^?2, V_oc=723 mV, FF=72.3 %). The dyes CM101 – CM104 show a broader spectral response compared with the reference dyes CMR101 – CMR104 and have high IPCE exceeding 90 % from 450 to 580 nm. Considering the reflection of sunlight, the photoelectric conversion efficiency could be almost 100 % during this region.     

Synthesis and Characterization of (2E,2 E)‐3,3‐((9,9‐diocyl‐9H‐flourene‐2,7‐diyl)bis(4,1‐phenylene))bis(2‐cyanoacylic acid) as a Symmetrical Metal‐free Organic Dye

In this study a novel symmetrical metal‐free organic dye for applications in dye‐sensitized solar cells (DSSCs) was synthesized. This dye ( D ) was designed with A–π–D–π–A framework and synthesized with 9,9‐dioctylfluorene as electron donor, phenylene as π‐spacer and cyanoacetic acid as electron acceptor. The chemical structure of product was determined using UV‐Vis, FT‐IR, CNMR, HNMR spectroscopy techniques. The presence of a phenylene π‐bridge between the donor and the acceptor units and the di‐anchoring moieties in this structure led to enhancement of conjugation lengths and molar extinction coefficient (ε) that is promising for further improvement of the conversion efficiency of DSSCs.