Pentacene

About: Pentacene is a research topic. Over the lifetime, 5051 publications have been published within this topic receiving 161481 citations. The topic is also known as: 2,3:6,7-dibenzanthracene & benzo[b]naphthacene.

The Low-Lying Electronic States of Pentacene and Their Roles in Singlet Fission

Abstract: We present a detailed study of pentacene monomer and dimer that serves to reconcile extant views of its singlet fission. We obtain the correct ordering of singlet excited- state energy levels in a pentacene molecule (E (S1 )< E (D)) from multireference calculations with an appropriate active orbital space and dynamical correlation being incorporated. In order to understand the mechanism of singlet fission in pentacene, we use a well-developed diabatization scheme to characterize the six low-lying singlet states of a pentacene dimer that approximates the unit cell structure of crystalline pentacene. The local, single-excitonic diabats are not directly coupled with the important multiexcitonic state but rather mix through their mutual couplings with one of the charge-transfer configurations. We analyze the mixing of diabats as a function of monomer separation and pentacene rotation. By defining an oscillator strength measure of the coherent population of the multiexcitonic diabat, essential to singlet fission, we find this population can, in principle, be increased by small compression along a specific crystal direction.

Organic thin-film transistors for organic light-emitting flat-panel display backplanes

Abstract: The performance of organic thin-film transistors (OTFTs) has improved significantly in the last several years and it now appears likely that they will find application in low-cost large-area electronic applications. Active-matrix displays are of special interest and integration of OTFTs with organic light-emitting devices (OLEDs) in all-organic displays is particularly attractive. The device requirements for active-matrix OLED displays are very similar to those of active-matrix liquid crystal displays (AMLCDs) and can be satisfied with OTFTs fabricated using stacked pentacene active layers. Such devices have demonstrated field-effect mobility near 1.5 cm/sup 2//V/spl middot/s, on/off current ratio near 10/sup 8/, near-zero threshold voltage, and subthreshold slope less than 1.6 V/decade. These characteristics are similar to those obtained with hydrogenated amorphous silicon (a-Si:H) devices and such devices would allow the use of polymeric substrates with advantages in weight, ruggedness, and cost compared to glass substrates currently used with a-Si:H devices in AMLCDs.

Amorphouslike density of gap states in single-crystal pentacene.

Abstract: We show that optical and electrical measurements on pentacene single crystals can be used to extract the density of states in the highest occupied molecular orbital-lowest unoccupied molecular orbital band gap. It is found that these highly purified crystals possess band tails broader than those typically observed in inorganic amorphous solids. Results on field-effect transistors fabricated from similar crystals imply that the gap state density is much larger within 5-10 nm of the gate dielectric. Thus, organic thin-film transistors for such applications as flexible displays might be significantly improved by reducing these defects.

Transparent flexible organic transistors based on monolayer graphene electrodes on plastic.

Abstract: There has been much interest in graphene-based electronic devices because graphene provides excellent electrical, optical, and mechanical properties. [ 1 ] In this sense, organic electronic devices using graphene electrodes have attracted considerable attention, and several reports have described the use of graphene source/drain electrodes in organic fi eld-effect transistors (OFETs). [ 2 ] One of the ultimate goals in the fabrication of OFETs using graphene electrodes lies in the fabrication of fl exible and transparent organic transistors, assembled on plastics substrates, that maintain their high performance under ambient conditions. However, no reports have described the fabrication of organic transistors assembled on plastic substrates because the synthesis of either graphene or reduced graphene oxide requires high-temperature fabrication processes. Another important goal in the context of fabricating organic electronic devices with graphene electrodes lies in the fabrication of highly transparent graphene electrodes that cover large areas. Graphene transmittance decreases linearly as the number of layers increases in n-layer graphene. [ 3 ] Thus, the use of monolayer graphene is necessary to achieve high transparency in graphene electrodes, provided that the conductivity of the graphene is suffi cient for device electrode applications. Another merit of monolayer graphene is its extremely low thickness (3–4 Å). Source/drain electrodes in staggered bottomcontact FET structures should be thin to ensure step coverage of the active layer during sequential transistor fabrication. [ 4 ] For this reason, one-atom-thick monolayer graphene provides ideal source/drain electrodes for effi cient charge injection. Recently, several groups succeeded in fabricating high-quality/largearea graphene with preferential monolayer thickness using a

Hole mobility in organic single crystals measured by a "flip-crystal" field-effect technique

Abstract: We report on single crystal high mobility organic field-effect transistors (OFETs) prepared on prefabricated substrates using a "flip-crystal" approach. This method minimizes crystal handling and avoids direct processing of the crystal that may degrade the FET electrical characteristics. A chemical treatment process for the substrate ensures a reproducible device quality. With limited purification of the starting materials, hole mobilities of 10.7, 1.3, and 1.4 cm^2/Vs have been measured on rubrene, tetracene, and pentacene single crystals, respectively. Four-terminal measurements allow for the extraction of the "intrinsic" transistor channel resistance and the parasitic series contact resistances. The technique employed in this study shows potential as a general method for studying charge transport in field-accumulated carrier channels near the surface of organic single crystals.