Hydrostatic-pressure dependence of the photoconductivity of single-crystal pentacene and tetracene

Rang, Zhenlin; Haraldsson, Anders; Kim, Dong M.; Ruden, P. P.; Nathan, M. I.; Chesterfield, Reid J.; Frisbie, C. Daniel

doi:10.1063/1.1410878

Cited by 55 publications

(44 citation statements)

References 12 publications

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“…The increase in the transfer integral is accompanied by the increase of the bandwidth of the HOMO and LUMO leading to a reduction in the band gap. Furthermore, the increase in the transfer integral leads to an increase in the mobility of charge carriers in accord with the experimental observation [21].…”

Section: Pressure Dependence Of Dielectric Constantsupporting

confidence: 88%

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A first-principles study of the vibrational properties of crystalline tetracene under pressure

Abdulla

Refson

Friend

et al. 2015

J. Phys.: Condens. Matter

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We present a comprehensive study of the hydrostatic pressure dependence of the vibrational properties of tetracene using periodic density-functional theory (DFT) within the local density approximation (LDA). Despite the lack of van der Waals dispersion forces in LDA we find good agreement with experiment and are able to assess the suitability of this approach for simulating conjugated organic molecular crystals. Starting from the reported Xray structure at ambient pressure and low temperature, optimised structures at ambient pressure and under 280 MPa hydrostatic pressure were obtained and the vibrational properties calculated by the linear response method. We report the complete phonon dispersion relation for tetracene crystal and the Raman and infrared spectra at the centre of the Brillouin zone.The intermolecular modes with low frequencies exhibit high sensitivity to pressure and we report mode-specific Grüneisen parameters as well as an overall Grüneisen parameter γ=2.8.Our results suggest that the experimentally reported improvement of the photocurrent under pressure may be ascribed to an increase in intermolecular interactions as also the dielectric tensor.2

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Section: Pressure Dependence Of Dielectric Constantsupporting

confidence: 88%

“…[21] is due to both the improvement in mobility resulting from the increase of overlap of molecular wavefunctions in the ab* plane and the associated increase in the transfer integral, and to the increase of the photogenerated charge facilitated by the increase of the dielectric constant [23,61,62]. …”

Section: Pressure Dependence Of Dielectric Constantmentioning

confidence: 99%

A first-principles study of the vibrational properties of crystalline tetracene under pressure

Abdulla

Refson

Friend

et al. 2015

J. Phys.: Condens. Matter

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“…For tetracene, its polymorph 1 (P 1 ) also called the high-temperature polymorph [97,107], referred to as TETCEN in the Cambridge Structural Database (CSD) [108], is considered. This crystal is known to undergo a pressure-assisted transition to a different high-pressure or low-temperature polymorph (P 2 ) [29,[109][110][111][112][113], the study of which is beyond the scope of this work. This low-temperature polymorph has been successfully described within the TS method in Ref.…”

Section: A Lattice Geometry and Cohesive Energymentioning

confidence: 99%

Structural and excited-state properties of oligoacene crystals from first principles

et al. 2016

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Molecular crystals are a prototypical class of van der Waals (vdW) bound organic materials with excitedstate properties relevant for optoelectronics applications. Predicting the structure and excited-state properties of molecular crystals presents a challenge for electronic structure theory, as standard approximations to density functional theory (DFT) do not capture long-range vdW dispersion interactions and do not yield excited-state properties. In this work, we use a combination of DFT including vdW forces, using both nonlocal correlation functionals and pairwise correction methods, together with many-body perturbation theory (MBPT) to study the geometry and excited states, respectively, of the entire series of oligoacene crystals, from benzene to hexacene. We find that vdW methods can predict lattice constants within 1% of the experimental measurements, on par with the previously reported accuracy of pairwise approximations for the same systems. We further find that excitation energies are sensitive to geometry, but if optimized geometries are used MBPT can yield excited-state properties within a few tenths of an eV from experiment. We elucidate trends in MBPT-computed charged and neutral excitation energies across the acene series and discuss the role of common approximations used in MBPT.

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“…[9][10][11] The ncrease of mobility has been reported for pentacene at hydrostatic pressures in gigapascal range. 9 In order to investigate possible changes in carrier mobility, C-AFM was performed on 75 nm as-deposited and imprinted pentacene films as per AFM analysis. The average and rms currents of the as-deposited pentacene films were measured as 29.9 and 19.4 pA, respectively.…”

mentioning

confidence: 86%

“…This result is consistent with the work reported by Rang et al, who demonstrated hydrostatic pressure induced increase in photoconductivity in single crystal pentacene films up to 0.3 GPa, caused by the increasing overlap of the adjacent molecular orbitals caused by pressure induced decrease of the intermolecular distances. 9 Increased mobility allows for thicker acene layers in organic photovoltaics, which would aid improved efficiency due to enhanced light absorption. Furthermore, the potential for other electronic applications is significant such as organic thin film transistors.…”

mentioning

confidence: 99%

Enhanced photovoltaic performance in nanoimprinted pentacene-PbS nanocrystal hybrid device

Dissanayake

Adikaari

Silva

2008

Applied Physics Letters

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Pentacene and PbS nanocrystal bilayer photovoltaic devices are fabricated after the pentacene layer is subjected to nanoimprinting using a laser textured silicon stamp. Increased short circuit current densities are observed for the imprinted devices, which are attributed to increased charge mobility in the pentacene film caused by the decrease in the intermolecular distances during nanoimprinting. This work is consistent with previous reports where hydrostatic pressure induced mobility increases have been observed in polyacenes under gigapascal pressure regimes. It is believed that the pentacene film undergoes localized high pressures during nanoimprinting, giving rise to the increased hole mobilities. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2890848͔ Semiconducting organic materials are suitable for low cost, large area, and flexible optoelectronic device fabrication. Recent reports demonstrate up to 6% optical to electrical power conversion efficient organic photovoltaic devices designed using the bulk heterojunction architecture. 1 However, to increase the power conversion efficiency ͑ ͒ beyond the envisaged market entry figure of 10%, further enhancement of the photovoltaic device properties, such as short circuit current ͑J sc ͒, open circuit voltage ͑V oc ͒, and fill factor, is essential. Incorporation of semiconducting nanocrystals, which demonstrate size dependent band gaps into organic photovoltaics, can potentially increase the light absorption from a wider part of the terrestrial solar spectrum. Such hybrid photovoltaic devices demonstrating light harvesting up to 1600 nm region have so far been reported in the literature. 2 These devices, however, operate at lower mainly due to poor charge transport properties of the nanocrystals and unfavorable energy level offsets between the donor-acceptor active layers. In an attempt to rectify these shortcomings, promising device architectures consisting of small molecule organic dyes ͑pentacene͒ and infrared absorbing PbS nanocrystals ͑ns-PbS͒ have been investigated. 3,4 Alternatively, power conversion efficiency of organic photovoltaic devices can be increased by enhancing exciton dissociation at the heterojunction through nanostructuring. Recent reports indicate up to twofold increase in the J sc of pentacene/ C 60 bilayer devices nanostructured by a technique involving nanoimprinted lithography ͑NIL͒. 5 We report incorporation of the NIL technique to increase the device performance of the pentacene/nc-PbS hybrid device architecture. We observe that J sc increases remarkably by two orders of magnitude after nanoimprinting, which is attributed to an increased in the charge mobility within the hole transporting layer. It is proposed that alternative phenomena, such as increased exciton dissociation, are not facilitated by the imprinting conditions used for this work.Twice sublimed pentacene ͑99.99%͒ was purchased from H.W. Sands and used without further purification. nc-PbS were synthesized with a narrow size distribution according to a method repo...

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Hydrostatic-pressure dependence of the photoconductivity of single-crystal pentacene and tetracene

Cited by 55 publications

References 12 publications

A first-principles study of the vibrational properties of crystalline tetracene under pressure

A first-principles study of the vibrational properties of crystalline tetracene under pressure

Structural and excited-state properties of oligoacene crystals from first principles

Enhanced photovoltaic performance in nanoimprinted pentacene-PbS nanocrystal hybrid device

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