Cyanoacetic Acid Acceptor Research Articles

Charge Transfer as Bridging Correlator for DSSC Efficiency and NLO Property

AbstractThe efficacy of dipyridyl and diphenylamine sensitizers in dye‐sensitized solar cells (DSSCs) is linked to trends in DFT‐based charge transfer and non‐linear optical (NLO) properties. We chose DFT and Time‐dependent‐DFT methods. The planarity is improved by replacing the phenyl ring at the donor site with a thiophene ring. Similarly, cyanoacetic acid acceptor improves planarity over rhodamine‐3‐acetic acid acceptor. In all cases in HOMO, the electron density is located at the donor and some part of the spacer, and in LUMO, it is shifted to the acceptor. Bond length alternation, bond order alternation, quinoid character, effective charge transferred distance, effective charge transferred, chemical potential, electrophilicity index, and electron correlation descriptors showed direct relation, while hardness and hyperhardness showed an inverse relation with NLO properties. We observed higher β0 and γ for thiophene‐based sensitizers ranging from 248.81×10−30 to 440.92×10−30 esu and 777.82×10−36 to 1442.69×10−36 esu, respectively. Likewise, more negative values of ΔGinject (−0.630 to −0.752 eV), a smaller value of ΔGreg (0.662 to 0.790 eV), and higher LHE (0.959 to 0.976) are observed for thiophene‐based sensitizers. Also, thiophene‐based sensitizers showed shorter Ti−O bond lengths than their phenyl‐based sensitizers. Photovoltaic parameters are directly related to DSSC efficiency and NLO properties.

Push-Pull Heterocyclic Dyes Based on Pyrrole and Thiophene: Synthesis and Evaluation of Their Optical, Redox and Photovoltaic Properties

Three heterocyclic dyes were synthesized having in mind the changes in the photovoltaic, optical and redox properties by functionalization of 5-aryl-thieno[3,2-b]thiophene, 5-arylthiophene and bis-methylpyrrolylthiophene π-bridges with different donor, acceptor/anchoring groups. Knoevenagel condensation of the aldehyde precursors with 2-cyanoacetic acid was used to prepare the donor-acceptor functionalized heterocyclic molecules. These organic metal-free dyes are constituted by thieno[3,2-b]thiophene, arylthiophene, bis-methylpyrrolylthiophene, spacers and one or two cyanoacetic acid acceptor groups and different electron donor groups (alkoxyl, and pyrrole electron-rich heterocycle). The evaluation of the redox, optical and photovoltaic properties of these compounds indicate that 5-aryl-thieno[3,2-b]thiophene-based dye functionalized with an ethoxyl electron donor and a cyanoacetic acid electron acceptor group/anchoring moiety displays as sensitizer for DSSCs the best conversion efficiency (2.21%). It is mainly assigned to the higher molar extinction coefficient, long π-conjugation of the heterocyclic system, higher oxidation potential and strong electron donating capacity of the ethoxyl group compared to the pirrolyl moiety.

Theoretical study of T shaped phenothiazine/carbazole based organic dyes with naphthalimide as π-spacer for DSSCs.

Eight novel T shaped phenothiazine/carbazole based organic dyes with naphthalimide as π-spacer were designed, and the geometries, electronic structures, and optical features of these isolated dyes and dye-(TiO2)9 systems were investigated with density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. Some quantify factors influencing the energy conversion efficiency (PCE) such as the light harvesting efficiency (LHE), electron injection driving force (ΔGinject) and dye regeneration driving force (ΔGreg) were also calculated for dye-sensitized solar cells (DSSCs) applications. It is found that these dyes show a good performance of electron injection and dye regeneration owing to the proper value of ΔGinject and ΔGreg. The optimized geometries of the non-planar molecular configuration of donor and the planar structure of the naphthalimide conjugated bridge are beneficial to efficient intramolecular charge transfer and the suppression of molecular aggregation. The properties about the electronic structure and absorption spectra indicate that replacement of benzene with thiophene unit near to cyanoacetic acid acceptor can generate more efficient conjugation effect and achieve red shift of absorption spectra, resulting a higher Jsc and Voc in DSSCs device. The theoretical results reveal that DTPH2, DTPH4, DTCA2 and DTCA4 would be used as potential sensitizers for DSSCs applications.

Cs -Symmetric Triphenylamine-Linked Bisthiazole-Based Metal-Free Donor-Acceptor Organic Dye for Efficient ZnO Nanoparticles-Based Dye-Sensitized Solar Cells: Synthesis, Theoretical Studies, and Photovoltaic Properties.

Herein, we have designed a metal-free donor–acceptor dye by incorporating an electron deficient bisthiazole moiety as a linker in between the electron donor triphenylamine and cyanoacetic acid acceptor. The bisthiazole-based organic dye D1 was synthesized using the Pd-catalyzed Suzuki cross-coupling and Knoevenagel condensation reactions. On the basis of the optical, electrochemical, and computational studies, dye D1 showed a better electronic interaction between the donor and acceptor moieties. As-synthesized C2 symmetric triphenylamine-linked bisthiazole-based organic dye D1 has four anchoring groups, which play a significant role for better adsorption on the ZnO surface along with the enhanced kinetics of photoexcited electron injection. Consequently, photovoltaic properties of the organic dye D1 has been carried out by fabricating the ZnO nanoparticles (ZnO NPs)-based solar device. We obtained the maximum incident photon-to-current conversion efficiency of about 56.20%, with a short-circuit photocurrent density (Jsc) of 13.60 mA cm–2, which results in a power conversion efficiency (PCE) of 4.94% under AM 1.5 irradiation (100 mW cm–2). The high PCE value is the result of proficient electron injection from ELUMO of dye D1 to the conduction band of ZnO NPs, as suggested by the computational calculations. Electrochemical impedance spectroscopy measurement is carried out to calculate the electron lifetime and also reveals the insight to the reduced charge recombinations at the various active interfaces of the photovoltaic device.

Asymmetric double donor-π-acceptor dyes based on phenothiazine and carbazole donors for dye-sensitized solar cells

Four organic dyes with asymmetric double donor-π-acceptor system were designed, synthesized and utilized in dye-sensitized solar cells (DSSCs), where phenothiazine and carbazole were introduced as double donors, butyl or octyl chain as the linker and cyanoacetic acid or rhodanine acetic acid as the electron acceptor. The design of double donor-π-acceptor system contributes to a distinctive increase of the molar extinction coefficient and benefits light-harvesting capability of these dyes. Due to superior electron injection efficiency, CPC-series dyes with cyanoacetic acid acceptor exhibit broader IPCE spectra and high IPCE responsive value compared with rhodanine-3-acetic acid acceptor, leading to higher JSC. Long alkyl chain favors antiaggregation effect and low charge recombination rate is observed for dyes with octyl chain which display higher VOC than those with butyl chain. Among four dyes, dye with octyl chain and cyanoacetic acid acceptor exhibits the highest short-circuit photocurrent density (9.64 mA cm−2) and open-circuit photovoltage (720 mV), leading to the best overall power conversion efficiency of 4.76%.

Electro-optical and charge injection investigations of the donor-π-acceptor triphenylamine, oligocene–thiophene–pyrimidine and cyanoacetic acid based multifunctional dyes

The corner stone of present study is to tune the electro-optical and charge transport properties of donor-bridge-acceptor (D-π-A) triphenylamine (TPA) derivatives. In the present investigation, an electron deficient moiety (pyrimidine), electron-rich moiety (thiophene) and oligocene (benzene, naphthalene, anthracene, tetracene and pentacene) have been incorporated as π-spacer between the donor TPA unit and cyanoacetic acid acceptor and anchoring group. The elongation of bridge usually affects the energy levels, i.e., higher the highest occupied molecular orbital (HOMO) while lower the lowest unoccupied molecular orbital (LUMO) thus reduces the HOMO–LUMO energy gap. The lowered LUMO energy levels of cyano-{2-[6-(4-diphenylamino-phenyl)-pyrimidin-4-yl]-tetraceno[2,3-b]thiophen-8-yl}-acetic acid (TPA-PTT4) and cyano-{2-[6-(4-diphenylamino-phenyl)-pyrimidin-4-yl]-pentaceno[2,3-b]thiophen-9-yl}-acetic acid (TPA-PPT5) dyes revealed that electron injected from dye to semiconductor surface might be auxiliary stable resulting in impediment of quenching. The broken co-planarity between the π-spacer conceiving LUMO and the TPA moiety would help to impede the recombination process. Moreover, it is expected that TPA derivatives with the tetracenothiophene and pentacenothiophene moieties as π-bridge would show better photovoltaic performance due to lowered LUMO energy level, higher electronic coupling constant, light harvesting efficiency and electron injection values.

Synthesis and density functional theory study of novel coumarin-type dyes for dye sensitized solar cells

Abstract A series of novel coumarin-type dyes were synthesized with coumarin donor, π bridges containing benzene and cyanoacetic acid or rhodanine acetic acid acceptor. The light-harvesting capabilities and photovoltaic performance of these dyes were investigated systematically. Moreover, density functional theory study of these coumarin dyes was performed. Among these compounds, dye with phenylthiophene bridge exhibits obvious superiority on optical and photovoltaic properties when compared with those of benzene or biphenyl bridge. Dyes bearing cyanoacetic acid acceptor have higher IPCE value and hence display better photovoltaic performance than those with rhodanine acetic acid acceptor. Dye with phenylthiophene bridge and cyanoacetic acid acceptor shows the most efficient photoelectricity conversion efficiency and has the maximum η value of 3.62% ( V oc = 660 mV, J sc = 7.72 mA/cm 2 , ff = 0.71) under simulated AM 1.5 irradiation (100 mW/cm 2 ).

Novel D–A–π–A carbazole dyes containing benzothiadiazole chromophores for dye-sensitized solar cells

New D–A–π–A carbazole dyes containing benzothiadiazole chromophores were designed and synthesized for application in dye-sensitized solar cells (DSSCs). The light-harvesting capabilities and photovoltaic performance of these dyes were investigated systematically through comparison of different π-bridges and acceptors. Compared with thiophene bridge, benzene bridge provides improved IPCE and VOC, which leads to better photoelectricity conversion efficiency. Dyes with cyanoacetic acid acceptor display superior photovoltaic properties though with shorter absorption maximum and lower molar absorption coefficient compared with dyes with rhodanine acetic acid acceptor. Therefore, dye with benzene bridge and cyanoacetic acid acceptor shows the most efficient photoelectricity conversion efficiency and has the maximum η value of 5.40% (VOC=710mV, JSC=10.99mA/cm2, and ff=0.71) under simulated AM 1.5 irradiation (100mW/cm2).

Engineering diketopyrrolopyrrole sensitizers for highly efficient dye-sensitized solar cells: enhanced light harvesting and intramolecular charge transfer

Two asymmetric DPP dyes with a D–π–A structure are reported, where DPP is used as a bridge to connect the triphenylamine donor and cyanoacetic acid acceptor.

Molecular engineering of panchromatic isoindigo sensitizers for dye-sensitized solar cell applications

A panchromatic dye was synthesized with an isoindigo core as a linker to bridge with a bis(4-tert-butylphenyl)phenylamine donor and a cyanoacetic acid acceptor for dye-sensitized solar cells, showing a broad spectral response and a high conversion efficiency of 7.55% under AM 1.5 conditions.

Cyanomethylbenzoic Acid: An Acceptor for Donor–π–Acceptor Chromophores Used in Dye‐Sensitized Solar Cells

Sensing the sun: Incorporation of a cyanomethyl benzoic acid electron acceptor into donor-π-acceptor sensitizers for dye-sensitized-solar cell is shown to lead to devices with improved conversion efficiency when compared with more widely used cyanoacetic acid acceptor.

Simple Triarylamine-Based Dyes Containing Fluorene and Biphenyl Linkers for Efficient Dye-Sensitized Solar Cells

New dipolar dyes featuring arylamine donors, fluorene or biphenyl conjugation, and cyanoacetic acid acceptor units have been synthesized and characterized by spectral, optical, and electrochemical measurements. Absorption measurements indicate that the fluorene conjugation is beneficial for red shifting the charge transfer transition and increasing the optical density. On the contrary, the biphenyl linker leads to a blue-shifted hypochromic charge-transfer transition due to the inefficiency in the π-conjugation. For a particular linker, the diphenylamine unit acts as an efficient donor when compared to the 1-naphthylphenylamine moiety. However, the red shift observed in the absorption profile for the diphenylamine-containing dyes is compensated for by a reduction in the molar extinction coefficient, that is, the naphthylamine derivatives are beneficial for increasing the molar extinction coefficient. Electrochemical investigations show that the fluorene-based dyes are more redox stable than the correspond...

Tuning the HOMO and LUMO Energy Levels of Organic Chromophores for Dye Sensitized Solar Cells

A series of organic chromophores have been synthesized in order to approach optimal energy level composition in the TiO2-dye-iodide/triiodide system in the dye-sensitized solar cells. HOMO and LUMO energy level tuning is achieved by varying the conjugation between the triphenylamine donor and the cyanoacetic acid acceptor. This is supported by spectral and electrochemical experiments and TDDFT calculations. These results show that energetic tuning of the chromophores was successful and fulfilled the thermodynamic criteria for dye-sensitized solar cells, electrical losses depending on the size and orientation of the chromophores were observed.