Unconventional, Chemically Stable, and Soluble Two-Dimensional Angular Polycyclic Aromatic Hydrocarbons: From Molecular Design to Device Applications

Zhang, L. and Cao, Y. and Colella, N. S. and Liang, Y. and Bredas, J. L. and Houk, K. N. and Briseno, A. L.. (2014) Unconventional, Chemically Stable, and Soluble Two-Dimensional Angular Polycyclic Aromatic Hydrocarbons: From Molecular Design to Device Applications. Accounts of Chemical Research, 48 (3). pp. 500-509.

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CONSPECTUS: Polycyclic aromatic hydrocarbons (PAHs), consisting of laterally fused benzene rings, are among the most widely studied small-molecule organic semiconductors, with potential applications in organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). Linear acenes, including tetracene, pentacene, and their derivatives, have received particular attention due to the synthetic flexibility in tuning their chemical structure and properties and to their high device performance. Unfortunately, longer acenes, which could exhibit even better performance, are susceptible to oxidation, photo-degradation, and, in solar cells which contain fullerenes, Die Is Alder reactions. This Account highlights recent advances in the molecular design of two-dimensional (2-D) PAHs that combine device performance with environmental stability. New synthetic techniques have been developed to create stable PAHs that extend conjugation in two dimensions. The stability of these novel compounds is consistent with Claes sextet rule as the 2-D PAHs have greater numbers of sextets in their ground-state configuration than their linear analogues. The ionization potentials (IPs) of nonlinear acenes decrease more slowly with annellation in comparison to their linear counterparts. As a result, 2-D bistetracene derivatives that are composed of eight fused benzene rings are measured to be about 200 times more stable in chlorinated organic solvents than pentacene derivatives with only five fused rings. Single crystals of the bistetracene derivatives have hole mobilities, measured in OFET configuration, up to 6.1 cm(2) V-1 s(-1), with remarkable I-on/I-off ratios of 10(7). The density functional theory (DFT) calculations can provide insight into the electronic structures at both molecular and material levels and to evaluate the main charge-transport parameters. The 2-D acenes with large aspect ratios and appropriate substituents have the potential to provide favorable interstack electronic interactions, and correspondingly high carrier mobilities. In stark contrast to the 1-D acenes that form mono- and bis-adducts with fullerenes, 2-D PAHs show less reactivity with fullerenes. The geometry of 2-D PAHs plays a crucial role in determining both the barrier and the adduct stability. The reactivity and stability of the 2-D PAHs with regard to Diels Alder reactions at different reactive sites were explained via DFT calculations of the reaction kinetics and of thermodynamics of reactions and simple Huckel molecular orbital considerations. Also, because of their increased stability in the presence of fullerenes, these compounds have been successfully used in OPVs. The small-molecule semiconductors highlighted in this Account exhibit good charge-transport properties, comparable to those of traditional linear acenes, while being much more environmentally stable. These features have made these 2-D PAHs excellent molecules for fundamental research and device applications.

Item Type: Article
Additional Information: ISI Document Delivery No.: CD8EBTimes Cited: 0Cited Reference Count: 51Zhang, Lei Cao, Yang Colella, Nicholas S. Liang, Yong Bredas, Jean-Luc Houk, K. N. Briseno, Alejandro L.Office of Naval Research N000141110636, N0001471410053, N000141110211; Center for Hierarchical Manufacturing CMMI-0531171; National Science Foundation CHE-1059084, CHE-1361104Collaboration between the UMass (L.Z., A.L.B.) and Georgia Tech groups (J.L.B.) is supported by the Office of Naval Research awards N000141110636, N0001471410053, and N000141110211. N.S.C. was supported by the Center for Hierarchical Manufacturing, (CMMI-0531171). K.N.H. is grateful to the National Science Foundation (CHE-1059084 and CHE-1361104) for financial support and the Extreme Science and Engineering Discovery Environment (XSEDE) for computer support.Amer chemical socWashington
Uncontrolled Keywords: mobility
Collections: Nanomanufacturing Research Collection > Nanomanufacturing Nanoscale Science and Engineering Centers > Center for Hierarchical Manufacturing
Depositing User: Robert Stevens
Date Deposited: 12 Nov 2015 18:18
Last Modified: 12 Nov 2015 18:18
URI: http://eprints.internano.org/id/eprint/2312

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