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Influence of Pendant Group on Mobility of Organic Thin Film Transistor in Correlation with Reorganization Energy of Molecules
摘要： Charge transport properties of common donor copolymers in organic photovoltaics, poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7-Th), with molecular structures differing only in the pendant group, are studied. This is the first report of field-effect transistor mobility (μFET) of PTB7-Th (0.14 cm2 V?1 s?1) and the highest μFET for PTB7 (0.01 cm2 V?1 s?1). μFET of PTB7-Th is found to be almost one order of magnitude higher than PTB7. To understand the influence of molecular structure on charge transport, hole reorganization energy (λh) is calculated from first-principles. λh of PTB7-Th (≈150 meV) is found to be lower than PTB7 (≈346 meV). Further, the ratio of hopping rate versus square of charge transfer integral calculated from Marcus theory using λh for these systems is found to indicate a higher rate of hole transfer across dimers or homojunction interface for PTB7-Th. These results are supplemented by experimentally determined λ using bulk-heterojunction organic solar cells, where λPTB7-Th≈200 meV and λPTB7≈310 meV follow a similar trend. The effective hole-mobility estimation from BHJ devices correlates well with these λ values. This study provides understanding of charge transport properties via reorganization energy, as a function of pendant group without altering the backbone of the chains.
关键词： OFET,mobility,reorganization energy,pendant groups
更新于2025-09-23 15:23:52
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Photoelectron Spectroscopy of Molecular Anion of Alq <sub/>3</sub> : An Estimation of Reorganization Energy for Electron Transport in the Bulk
摘要： A molecular anion of tris(8-hydroxyquinolinato)aluminum (Alq3) was generated by a pulsed discharge to the solid sample under supersonic expansion and its photoelectron spectrum was recorded after mass selection. The vertical detachment energy of Alq3? and the adiabatic electron affinity of Alq3 were determined to be 1.24 ± 0.01 and 0.89 ± 0.04 eV, respectively. By using these energies determined for monomeric Alq3, the reorganization energy for the intermolecular electron transport in bulk Alq3 was estimated to be 0.70 ± 0.08 eV.
关键词： Photoelectron Spectroscopy,Electron Transport,Reorganization Energy,Alq3,Molecular Anion
更新于2025-09-23 15:21:21
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A computational study on boron dipyromethene ancillary acceptor-based dyes for dye-sensitized solar cells
摘要： A series of (D-π)2-An-A based organic dyes containing boron dipyrromethene (BODIPY) moiety as an ancillary acceptor (An) derivative were chosen, and the effect of donor moieties (diarylamine, carbazole, azepine, and dibenzazepine) was investigated to understand their photophysical and photoelectrochemical properties by employing density functional theory (DFT) and time-dependent DFT. It is experimentally proved that BODIPY enhances the light-harvesting in red and near IR region of visible light. The electron density distribution analysis was performed for all the dyes to confirm the intramolecular charge transfer, envisioned from the simulated absorption spectra of the dyes. Carbazole donor-based dye exhibited the lowest reorganization energy. A dye attached to the TiO2 (1 0 1) surface was modeled to estimate the adsorption energy of the dyes. The density of states analysis revealed that the absence of defect states in the bandgap of TiO2 facilitates the smooth electron transfer from the excited state of the dye to the conduction band of TiO2. Considering the lowest unoccupied molecular orbital (LUMO) energy level of dyes and conduction band energy level of TiO2, it is understood that all the dyes studied in this study are capable of electron injection upon photoexcitation. Considering the driving force for dye regeneration of the dyes and the magnitude of reorganization energy, carbazole donor-based dye (D2) would be the best performing dye in DSSC. Previously, the power conversion efficiencies of the dyes have been reported, and carbazole donor-based dye (D2) exhibited the highest efficiency among all the dyes. Our computational investigations are in good agreement with the experimental results.
关键词： TiO2 (1 0 1) surface,Reorganization energy,DSSC,Dye regeneration,BODIPY
更新于2025-09-23 15:21:01
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A quantitative structure–property study of reorganization energy for known p-type organic semiconductors
摘要： Intramolecular reorganization energy (RE), which quantifies the electron-phonon coupling strength, is an important charge transport parameter for the theoretical characterization of molecular organic semiconductors (OSCs). On a small scale, the accurate calculation of the RE is trivial; however, for large-scale screening, faster approaches are desirable. We investigate the structure–property relations and present a quantitative structure–property relationship study to facilitate the computation of RE from molecular structure. To this end, we generated a compound set of 171, which was derived from known p-type OSCs built from moieties such as acenes, thiophenes, and pentalenes. We show that simple structural descriptors such as the number of atoms, rings or rotatable bonds only weakly correlate with the RE. On the other hand, we show that regression models based on a more comprehensive representation of the molecules such as SMILES-based molecular signatures and geometry-based molecular transforms can predict the RE with a coefficient of determination of 0.7 and a mean absolute error of 40 meV in the library, in which the RE ranges from 76 to 480 meV. Our analysis indicates that a more extensive compound set for training is necessary for more predictive models.
关键词： molecular signatures,molecular transforms,reorganization energy,organic semiconductors,quantitative structure–property relationship
更新于2025-09-19 17:15:36
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Designing alkoxy-induced based high performance near infrared sensitive small molecule acceptors for organic solar cells
摘要： Scientist are dedicated to design and synthesize efficient photovoltaic materials to overcome the energy crises. In this regard, herein, we have designed four new small acceptor molecules namely (A1, A2, A3 and A4) for better performance in organic solar cells. These molecules consist Alkoxy-Induced Naphtho-dithiophene core unit flanked with 2,2-ethylidene-5,6-dicyano-3-oxo-2,3-dihydroinden-1-ylidene-malononitrile (A1), methyl-2-cyano-2,2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene-acetate (A2), 5,2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene-3-methyl-2-thioxothiazolidin-4-one (A3) and 2,5-ethylidene-6-oxo-5,6-dihydrocyclopenta-thiophen-4-ylidene-malononitrile (A4) end-capped acceptor groups. Their optical, electrical and geometries have been compared with reported molecule R. Frontier molecular orbital diagram reveal excellent charge transfer rate, The electron density is shifted from donor to acceptor unit. Among all, A1 exhibits the highest absorption in the visible region (λmax) at 798 nm in chloroform solvent. The maximum open circuit voltage (2.08 V) is observed for A3 when blended with PTB7-Th donor polymer. All studied molecules have high charge mobilities due to lower reorganization energy values with respect to model molecule R. A1 has the highest electron mobility among all molecules due to lower value of reorganization energy which is 0.0034. Furthermore, all designed molecules show good Solubilities in organic solvent. A2 exhibit high value of dipole moment which reveal good solubilities in fabrication process.
关键词： Transition density matrix,Non-fullerene acceptor,Open circuit voltages,Naphtho-dithiophene,Reorganization energy,Fused ring electron acceptor
更新于2025-09-19 17:13:59
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Synthesis, characterization and the photoinduced electron-transfer energetics of CdTe/CdSe type-II core/shell quantum dots
摘要： The CdTe/CdSe type-II core/shell quantum dots (QDs) were chemically synthesized in a noncoordinating solvent. The optical properties and structures of the synthesized QDs were characterized by absorption spectroscopy (Abs), photoluminescence (PL) spectroscopy, PL-decay lifetime, X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The PL peak of the CdTe/CdSe core/shell QDs could be tuned from 698 nm (1.77 eV) to 780 nm (1.59 eV) by changing the thickness of CdSe shell and fixing the size of CdTe core. The PL quantum yields (QYs) of these QDs were from 14.1% to 31.7% and their full width at half maximum (FWHM) of PL peaks was kept below 0.12 eV during the growth process of CdSe shell on CdTe core. Compared to CdTe cores, the CdTe/CdSe type-II core/shell QDs have much longer PL decay times, up to ~100 ns. Based on Marcus theory, the charge transfer (CT) of CdTe/CdSe 1-5 monolayers (MLs) type-II core/shell QDs has been studied and the effects of quantum confinement on the structure parameters have been revealed. The reorganization energies (RE) of the CdTe/CdSe (1-5 ML) type-II core/shell QDs for the electron transfer (ET) were in the range from 60 meV to 106 meV and was found that ET takes place in the Marcus inverted region (-?G0 ET > λCT) which is typical for these QDs.
关键词： core/shell,reorganization energy,type-II quantum dots,spatial separations,CdTe/CdSe
更新于2025-09-19 17:13:59
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Tuning opto-electronic properties of alkoxy-induced based electron acceptors in infrared region for high performance organic solar cells
摘要： Limitations of fullerene-based acceptors for organic solar cell have driven the scientific community to design and synthesize non-fullerene acceptors. In this regard, we have designed four new molecules designated here S1-S4 containing Alkoxy-Induced Naphtho-dithiophene donor unit and 2-(5,6-difluoro-2-methylene-3-xo-2,3-dihydrinden-1-ylidene)malonoitrile acceptor moiety attached with different bridge units. The electronic and optical properties of the designed molecules S1-S4 are compared with the recently reported reference molecule R. The bridge units are, thiophene (S1), 2-fluorothiophene (S2), 2-(thiophe-2-yl)thiophene (S3) and 2-(4-fluorothiophen-2-yl)thiophene (S4). The designed molecule S3 shows absorption maximum in near infra-red (NIR) region at 830.0 nm and 910.6 nm in gas phase and chloroform solvent, respectively. The energy gaps of designed molecules are lower than that of the reference R, which reveal high charge transfer for the designed molecules. Among all, S3 has the lowest energy gap (1.68 eV). Open circuit voltages (Voc) calculation are performed with well-known PTB7-Th donor. Voc of all the molecules are higher than R where the maximum Voc of 1.92V is calculated for S2. Low reorganization energies of our designed molecule reflect high charge transfer rate with respect to R. Among all designed molecules, S3 has the highest electron mobility.
关键词： Alkoxy induced,Reorganization energy,Transition density matrix,Non-fullerene acceptor,Thiophene,Charge Transfer,Open circuit voltages
更新于2025-09-19 17:13:59
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Designing dithienonaphthalene based acceptor materials with promising photovoltaic parameters for organic solar cells
摘要： Scientists are focusing on non-fullerene based acceptors due to their efficient photovoltaic properties. Here, we have designed four novel dithienonaphthalene based acceptors with better photovoltaic properties through structural modification of a well-known experimentally synthesized reference compound R. The newly designed molecules have a dithienonaphthalene core attached with different 2-(5,6-difluoro-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (H1), 2-(5,6-dicyano-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile (H2), 2-(5-methylene-6-oxo-5,6-dihydrocylopenta[c]thiophe-4-ylidene)-malononitrile (H3) and 2-(3-(dicyanomethylene)-2,3-dihydroinden-1-yliden)malononitrile (H4) acceptor moieties (end-capped). The photovoltaic parameters of the designed molecules are discussed in comparison with those of the reference R. All newly designed molecules show a reduced HOMO–LUMO energy gap (2.17 eV to 2.28 eV), compared to the reference R (2.31 eV). Charger transfer from donor to acceptor is confirmed by a frontier molecular orbital (FMO) diagram. All studied molecules show extensive absorption in the visible region and absorption maxima are red-shifted compared to R. All investigated molecules have lower excitation energies which reveal high charge transfer rates, as compared to R. To evaluate the open circuit voltage, the designed acceptor molecules are blended with a well-known donor PBDB-T. The molecule H3 has the highest Voc value (1.88 V). TDM has been performed to show the behaviour of electronic excitation processes and electron hole location between the donor and acceptor unit. The binding energies of all molecules are lower than that of R. The lowest is calculated for H3 (0.24 eV) which reflects the highest charge transfer. The reorganization energy value for both the electrons and holes of H2 is lower than R which is indicative of the highest charge transfer rate.
关键词： absorption maxima,binding energies,reorganization energy,photovoltaic properties,open circuit voltage,charge transfer,dithienonaphthalene,HOMO–LUMO energy gap,non-fullerene based acceptors
更新于2025-09-12 10:27:22
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Tuning Optoelectronic Properties of Dithienopyrrole Donor Molecules for Organic Solar Cells
摘要： Theoretical analysis of physical properties of organic solar cells (OSCs) are important in order to reveal the correlation between power conversion efficiencies (PCE), structure and properties. Five new A?D?A type small molecules M1, M2, M3, M4, and M5 were designed by using dithienopyrrole (DTP) as electron rich donor unit with different types of π-spacers and end capped acceptor units. Functional MPW1PW91/6-31G(d,p) level of theory was used to optimize the geometry of all molecules. For excited state calculation TD-MPW1PW91/6-31G(d,p) level of theory was used. The geometries, electronic structures, dipole moment, open circuit voltage, reorganization energies and charge transport properties of designed molecules (M1 M5) have been scrutinized comparing with the reported compound R. The results revealed that the HOMO energy levels of molecules M1, M2, M3, and M5 were lower while M4 was of high energy level thus facilitate the donation of electron as compared to references molecule R. While LUMO energy level of all the molecules were slightly high energy due electron withdrawing effects of spacer and acceptor moiety. Highest energy gap of HOMO–LUMO was observed in M1 which was 2.48 eV and M3 showed low energy gap (2.11 eV) as compared to other designed molecules. All molecules showed low values for λe, so they have high rate of electron transfer as compared to R. All designed molecules exhibited higher value of dipole moment as compared to reference molecule R except M1. Higher value of dipole moment of donor molecules contrary to reference means good solubility towards organic solvents which is beneficial for further solar cell device fabrication. All designed molecules show higher Voc values except M4 which has comparable Voc with respect to reference molecule R. In short, choice of appropriate electron withdrawing and donating groups is very important for improving power conversion efficiencies of OSCs.
关键词： Dithienopyrrole,reorganization energy,open circuit voltages,density of states,density functional theory
更新于2025-09-12 10:27:22
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Computational study on optoelectronic and charge transport properties of diketopyrrolopyrrole-based A–D–A–D–A structure molecules for organic solar cells
摘要： Eight novel diketopyrrolopyrrole (DPP)-based A–D–A–D–A structure molecules were designed for organic solar cells (OSCs) applications. In these molecules, the electron-deficient DPP and dicyanovinyl groups were used as the acceptor groups and different planar electron-rich groups were employed as the donor π-bridges. Applying the B3LYP/6–31G (d,p) and TD-B3LYP/6–31G (d,p) methods, the optoelectronic and charge transport properties were investigated. It turned out that the different π-bridges can tune effectively the frontier molecular orbital energy levels, band gap, and absorption spectra. Furthermore, the different π-bridges also affect the charge transport properties of the designed molecules. Our results suggest that the investigated molecules can serve as donor materials. Additionally, some investigated molecules can also be used as hole and/or electron transport materials for OSCs.
关键词： Optoelectronic property,Dicyanovinyl,Reorganization energy,Diketopyrrolopyrrole (DPP),Organic solar cells (OSCs)
更新于2025-09-12 10:27:22