Evolution of Electronic Structures of Polar Phthalocyanine–Substrate Interfaces

Mandal, Subhankar; Mukherjee, M.; Hazra, S.

doi:10.1021/acsami.0c12614

Cited by 17 publications

(16 citation statements)

References 41 publications

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“…Thus, the interaction with the Ag(111) substrate is reduced, leading to an increased VL, that is ~ 0.4 eV higher than that of the typical flat-on Cl-up configuration. This provides a useful avenue toward work function tuning of metal electrodes in organic-based devices 33 . The optomechanical process referred to here is different from precedent studies, in which photoisomerization effect caused the switch between cis and trans states to induce mechanical motion.…”

Section: Discussionmentioning

confidence: 99%

Optomechanical switching of adsorption configurations of polar organic molecules by UV radiation pressure

Arumugam

Goyal

Chen

et al. 2021

Sci Rep

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Using photoemission spectroscopy (PES), we have systematically investigated the behavior of polar organic molecule, chloroaluminum phthalocyanine (ClAlPc), adsorbed in the Cl-down configuration on the Ag(111) substrate at low temperature − 195 °C under UV irradiation with a range of different photon fluxes. Judging from the evolution of photoemission spectral line shapes of molecular energy states, we discovered that the Cl atoms are so robustly anchored at Ag(111) that the impinging photons cannot flip the ClAlPc molecules, but instead they crouch them down due to radiation pressure; we observe that the phthalocyanine (Pc) lobes bend down to interact with Ag atoms on the substrate and induce charge transfer from them. As photon flux is increased, radiation pressure on the Pc plane initiates tunneling of the Cl atom through the molecular plane to turn the adsorption configuration of ClAlPc from Cl-down to an upheld Cl-up configuration, elucidating an optomechanical way of manipulating the dipole direction of polar molecules. Finally, work function measurements provide a distinct signature of the resulting upheld Cl-up configuration as it leads to a large increase in vacuum level (VL), ~ 0.4 eV higher than that of a typical flat-on Cl-up configuration driven by thermal annealing.

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Section: Discussionmentioning

confidence: 99%

Optomechanical switching of adsorption configurations of polar organic molecules by UV radiation pressure

Arumugam

Goyal

Chen

et al. 2021

Sci Rep

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“…Topography of the PNC thin films (before and after TA) were mapped by an atomic force microscope (CSI Nano-Observer). , Topographic images were collected using Au coated Si tip (radius of curvature ∼10 nm) in a tapping mode (resonance frequency ∼60 kHz) to minimize tip-induced damage of the soft film. Scans of different sizes and in different portions of the sample were carried out to get statistically meaningful information about the topography.…”

Section: Methodsmentioning

confidence: 99%

Nanoparticle Mediated Improved Crystallinity and Connectivity of Semiconducting Polymer Thin Films

Saifuddin

Biswas

Roy

et al. 2023

ACS Appl. Polym. Mater.

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Polymer nanocomposites (PNCs), i.e., nanoparticle (NP) incorporated semiconducting polymers (SPs), constitute a class of active materials where the dispersion and locations of the NPs and the crystallinity of the SPs play important roles in deciding their device performances. Herein Au nanoparticle (AuNP) mixed poly(3-hexylthiophene) [P3HT] was taken as a model PNC system, and a unique combination of complementary techniques was utilized to address these dispersion-related structural issues, viz the organization and/or dispersion of AuNPs, its evolution with thermal annealing (TA), and their effects on the ordering or crystallization of the P3HT matrix. The layering of AuNPs near the interfaces, namely confined or near monolayer thick layer at the film−substrate interface and fluctuated or near bilayer thick layer at the film−air interface, are evident in the as-cast PNC thin films, indicating self-organization and phase separation tendencies of the similar and dissimilar materials (i.e., dominant decrease of enthalpic energy over entropy) and different (hard and soft) boundary conditions of the interfaces. On the other hand, appreciable dispersion of AuNPs inside P3HT matrix is evident after TA, suggesting thermal energy induced diffusion of AuNPs through amorphous P3HT regions, overcoming the selforganization and phase separation (i.e., dominant increase of entropic energy over enthalpy). Such dispersion enhances the quantity (fraction or amount) and quality (planarity or conjugation length) of P3HT crystallites (and thus validates the dispersion of AuNPs in the amorphous P3HT regions) and their edge-on orientation and connectivity. This information or understanding is very useful for optimizing the structures of the PNC-based active layers for their better charge carrier mobility and device performances.

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“…Incorporation of a molecular layer between a metal and an organic semiconducting layer is one such interesting tool to engineer the energy levels at the metal–semiconductor interface. , An interfacial molecular layer of polar molecule is of particular interest as it can form a net dipole moment through organization of the molecules in a particular orientation. The molecular dipole layer was found to form on the metal surface through controlled deposition and thermal annealing of the polar molecules, such as chlorogallium phthalocyanine (ClGaPc). , The resultant dipole direction of such a layer was, however, found to depend on the adsorption geometry of the molecules on that specific metal surface (as shown schematically in Figure ). , Incorporation of such a molecular dipole layer, which can tune and/or align the molecular energy levels at the metal-DNTT interface, has not been studied so far.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dipole Layer and Alkyl Side-Chain Induced Improvement in the Energy Level Alignment and Wetting of Dinaphthothienothiophene Thin Films

Mandal,

Jana,

Roy

et al. 2023

J. Phys. Chem. C

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The evolution of electronic structures and morphology of dinaphthothienothiophene (DNTT) thin films on highly oriented pyrolytic graphite, due to the incorporation of a polar chlorogallium phthalocyanine (ClGaPc) molecular layer at the interface, substitution of DNTT with alkyl side-chain-incorporated S-shaped DNTT (S-DNTT-C10), and thermal annealing, were investigated using photoelectron spectroscopic techniques to check the possibility of proper energy level alignment at the metal− organic interface, which is one of the key challenges to improve the charge transport in organic semiconductor-based devices. A significant modulation in the vacuum level (VL) and a small downward shift in the highest occupied molecular orbital (HOMO) level with an intermediate charge injection level (CIL) are evident in the DNTT thin film due to the incorporation of the ClGaPc layer at the interface. This is a clear signature of the molecular dipole layer (of well-ordered Cl-up orientated ClGaPc molecules)-induced realignment of the molecular energy levels of the DNTT thin films. On the other hand, a noticeable downward shift in the VL, a signature of an improvement in the bulk coverage, is evident in the S-DNTT-C10 film, which can be attributed to the presence of aliphatic hydrocarbons in the alkyl side-chain incorporated molecule. Furthermore, a double-peak-like HOMO level is evident in the S-DNTT-C10 film, which can be attributed to the two distinct orientations/arrangements of the molecules, one at the interface and other in the remaining part of the film. The formation of an intermediate CIL, through incorporation of a molecular dipole layer at the interface, is helpful to overcome the large hole injection barrier, while the enhancement of molecular coverage at the metal−organic interface and thereafter, through molecular engineering, is useful to increase the hole injection area, both of which are of immense importance in improving the device performances.

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Evolution of Electronic Structures of Polar Phthalocyanine–Substrate Interfaces

Cited by 17 publications

References 41 publications

Optomechanical switching of adsorption configurations of polar organic molecules by UV radiation pressure

Optomechanical switching of adsorption configurations of polar organic molecules by UV radiation pressure

Nanoparticle Mediated Improved Crystallinity and Connectivity of Semiconducting Polymer Thin Films

Molecular Dipole Layer and Alkyl Side-Chain Induced Improvement in the Energy Level Alignment and Wetting of Dinaphthothienothiophene Thin Films

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