Classical simulation of deposition of thiophene oligomers on TiO2-anatase: Relevance of long-range electrostatic interactions

Alves-Santos, Marcelo; Caldas, M. J.

doi:10.1016/j.synthmet.2009.08.033

Cited by 6 publications

(8 citation statements)

References 19 publications

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“…The molecular arrangement inferred for the glass/P3HT interface agrees with the wide distribution of molecular orientations for the P3HT/TiO 2 interface, obtained from computer simulations. 65 At the SC-type Al/P3HT interface, the determined molecular orientation may explain the absence of spontaneous charge transfer to the metal. On the basis of the MO model with a V-shaped conformation, P3HT chains are found to order tightly with θ ≈ 85°and ϒ ≈ 85°.…”

Section: Resultsmentioning

confidence: 98%

Molecular Ordering of Conjugated Polymers at Metallic Interfaces Probed by SFG Vibrational Spectroscopy

Maia

Miranda

2015

J. Phys. Chem. C

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Organic−metal interfaces play a fundamental role in charge injection to organic electronic devices, and their performance significantly affects the device efficiency. Therefore, these interfaces have been studied by numerous experimental techniques, but most of them are either not strictly interface-specific or require special samples, with ultrathin metal or molecular coatings, which may not be representative of real devices. Here we use sum-frequency generation vibrational spectroscopy (SFG-VS), a surface-specific tool based on nonlinear optics, to probe the molecular arrangement of conjugated polymers (CPs) at metallic interfaces with architectures that are typical of organic devices. The CPs investigated were the widely used poly(3-hexylthiophene) (P3HT) and poly(octylfluorene) (PF8), in contact with either gold (Au) or aluminum (Al). On the basis of a simple model for the optical nonlinearity of polymer chains, we were able to quantitatively determine the orientation of CP chains at metallic interfaces. The results show that the polymer orientation is different in the two types of CP−metal interfaces (CP spin-coated on metal or metal thermally evaporated on the CP film), but in all of them the polymer backbone is not planar, on average, having a preferential torsion either toward or away from the interface. For PF8/Au interfaces, SFG spectra are reported for the first time and indicate spontaneous charge transfer. For the interfaces between PF8 and Al, the polymer chains are nearly parallel to the substrate, with the conjugated rings lying almost flat on the surface. Although charge transfer to/from the metal would be favored by this molecular configuration, the SFG spectra suggest the absence of polymer doping, which may be explained by the coincidence of Fermi levels for Al and PF8. In the case of P3HT, the chains are either quite parallel to the interface for polymer-on-metal samples, with thiophene rings nearly perpendicular to the metal substrates (edge-on orientation), or quite tilted from the interface, mainly exposing their ends to the metal, for thermally evaporated metal-on-polymer samples. For both P3HT/Al and P3HT/Au interfaces, SFG spectra indicate that spontaneous charge transfer is hindered by these molecular arrangements. These results may shed light on the mechanisms for charge injection across organic/metal interfaces and could also guide the design of novel organic devices with molecularly tailored interfaces to improve their efficiency.

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Section: Resultsmentioning

confidence: 98%

Molecular Ordering of Conjugated Polymers at Metallic Interfaces Probed by SFG Vibrational Spectroscopy

Maia

Miranda

2015

J. Phys. Chem. C

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“…The specific orientation of the polymer on the surface was chosen from atomistic CMD simulations of deposition of thiophene oligomers (α-T4) on the (101) oxide surface; the methodology is described elsewhere. 25 Our CMD results show the formation of a rough film with height comparable to the length of the oligomer. The analysis of the film shows that the majority of the molecules have orientation between 60°and 80°, "standing" on the surface as seen in experimental data.…”

Section: Models and Methodologymentioning

confidence: 56%

Section: Models and Methodologymentioning

confidence: 99%

“…Nonbonded interactions are of prime relevance when dealing with adsorbed structures, and at this time there are several different schemes , for adding van der Waals corrections to DFT structural optimizations. However, our focus here is on band alignments, which should not be compromised by slight differences in the molecule–surface adsorption geometry; thus, we opted for taking all structural properties from the same CMD methodology, carefully tested for this system …”

Section: Models and Methodologymentioning

confidence: 99%

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Electronic Structure of Interfaces between Thiophene and TiO₂ Nanostructures

et al. 2014

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We investigated the electronic properties of hybrid combinations of organic−inorganic interfaces relevant for photovoltaic applications, a thiophene (molecule or polymer) and a TiO 2 -anatase nanostructure, using ab initio density functional theory (DFT) and many-body perturbation theory calculations for model systems. The DFT results concerning electronic charge distribution show interface states coupling the polymer to the oxide substrate at the molecule's lowest unoccupied state, favoring electron transfer from the organic to the oxide through photoexcitation. Concerning the energy level structure, DFT predicts a virtually zero effective energy gap between polymer valence and oxide conduction bands. The GW-based results lead to proper band alignment, restoring the interface energy gap, and at the same time highlight the confinement effects to be expected for oxide nanostructures.

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“…Abaixo, na figura 2.14, apresentamos distorções típicas que levam a concavidade (movimento do segundo anel Desta forma, para o fulereno os parâmetros utilizados foram desenvolvidos em trabalho anterior [51,52]. Para os sistemas de oligotiofenos reparametrizamos a parte não-ligada das interações, e também a energia de interação ligada associada ao potencial de torção do diedro central do backbone de tiofeno, cuja descrição no contexto do UFF tambémé verificado ser incorreta [64,65]. Neste capítulo apresentamos a validação do NUFF para estes sistemas.…”

Section: P3ht: Orientação Relativa De Anéis Ligadosunclassified

Estudo atomístico da desordem eletrônica em filmes amorfos de polímeros conjugados

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Classical simulation of deposition of thiophene oligomers on TiO2-anatase: Relevance of long-range electrostatic interactions

Cited by 6 publications

References 19 publications

Molecular Ordering of Conjugated Polymers at Metallic Interfaces Probed by SFG Vibrational Spectroscopy

Molecular Ordering of Conjugated Polymers at Metallic Interfaces Probed by SFG Vibrational Spectroscopy

Electronic Structure of Interfaces between Thiophene and TiO₂ Nanostructures

Estudo atomístico da desordem eletrônica em filmes amorfos de polímeros conjugados

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Classical simulation of deposition of thiophene oligomers on TiO2-anatase: Relevance of long-range electrostatic interactions

Cited by 6 publications

References 19 publications

Molecular Ordering of Conjugated Polymers at Metallic Interfaces Probed by SFG Vibrational Spectroscopy

Molecular Ordering of Conjugated Polymers at Metallic Interfaces Probed by SFG Vibrational Spectroscopy

Electronic Structure of Interfaces between Thiophene and TiO2 Nanostructures

Estudo atomístico da desordem eletrônica em filmes amorfos de polímeros conjugados

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Electronic Structure of Interfaces between Thiophene and TiO₂ Nanostructures