Two novel dioxolane-substituted pentacene derivatives, namely, 6,14-bis-(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (TP-5) and 2,2,10,10-tetraethyl-6,14-bis-(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (EtTP-5), have been synthesized and spectroscopically characterized. Here, we examine the steady-state and time-resolved photoluminescence (PL) of solid-state composite films containing these pentacene derivatives dispersed in tris(quinolin-8-olato)aluminum(III) (Alq(3)). The films show narrow red emission and high absolute photoluminescence quantum yields (phi(PL) = 59% and 76% for films containing approximately 0.25 mol % TP-5 and EtTP-5, respectively). The Förster transfer radius for both guest-host systems is estimated to be approximately 33 A. The TP-5/Alq(3) thin films show a marked decrease in phi(PL) with increasing guest molecule concentrations, accompanied by dramatic changes in the PL spectra, suggesting that intermolecular interactions between pentacene molecules result in the formation of weakly radiative aggregates. In contrast, a lesser degree of fluorescence quenching is observed for EtTP-5/Alq(3) films. The measured fluorescence lifetimes of TP-5 and EtTP-5 are similar (approximately 18 ns) at low concentrations but deviate at higher concentrations as aggregation begins to play a role in the TP-5/Alq(3) films. The onset of aggregation in EtTP-5/Alq(3) films occurs at higher guest molecule concentrations (>1.00 mol %). The addition of ethyl groups on the terminal dioxolane rings leads to an increase in the intermolecular spacing in the solid, thereby reducing the tendency for pi-pi molecular stacking and aggregation.

New N,N′-substituted 1,4,5,8-naphthalene tetracarboxylic diimides (NTCDIs) were synthesized in one step reactions, resulting in excellent electron mobilities in air as measured in organic field effect transistors (OFETs). Two perfluoroalkyl-benzyl N,N′ substituents were used, differing in the length of the perfluoroalkyl moieties on the benzyl portion of the molecule. Single crystals of the short chain compound 2 were successfully grown by horizontal vapor deposition, and crystal structures were obtained and analyzed. Devices from both compounds were fabricated on untreated and silane treated Si/SiO2 substrates. The longer chain compound 1 gives the largest field effect mobility, reaching 0.57 cm2/(V s) in air. This is competitive with the best air stable n-channel materials to date. In contrast to previously studied high mobility materials, 1 achieved mobilities near 0.4 cm2/(V s) without the use of dielectric substrate treatments. Additionally, 1 displays exemplary ordering regardless of surface treatment, as determined from X-ray diffraction, while 2 displays significant improvement in mobility and film structure when deposited on surface treated substrates.

Organic light‐emitting diodes (OLEDs) containing red‐light‐emitting dioxolane‐substituted pentacene derivatives are fabricated and characterized. The OLEDs feature guest–host emitting layers consisting of either 6,14‐bis(triisopropylsilylethynyl)‐1,3,9,11‐tetraoxa‐dicyclopenta[b,m]pentacene (TP‐5) or 2,2,10,10‐tetraethyl‐6,14‐bis(triisopropylsilylethynyl)‐1,3,9,11‐tetraoxa‐dicyclopenta[b,m]pentacene (EtTP‐5) dispersed in tris(quinolin‐8‐olato) aluminum(III) (Alq3). High external electroluminescence (EL) quantum efficiency (ηEL = 3.3 %), not far from the theoretical limit, is observed for an OLED device based on a dilute EtTP‐5:Alq3 emitting layer (0.25 mol % EtTP‐5). The proposed EL mechanism is a combination of Förster energy transfer and direct electron–hole recombination on the guest pentacene molecules, as inferred by changes in the EL versus photoluminescence spectra and the positions of the highest occupied molecular orbital and lowest unoccupied molecular orbital gap of the guest within that of the host (estimated via cyclic voltammetry). Further evidence of charge trapping is provided by increased operational voltages at increased guest‐molecule concentration.

We have prepared a series of trialkylsilylethynylated anthracenes (a-d) to investigate the effects of solid-state interactions and acene substitution on the electroluminescence spectra of OLED devices. We designed these materials to have differing amounts of -face interactions and various film morphologies. We were particularly interested in intermolecular interactions between aromatic faces, which would manifest in the electroluminescence spectrum as a bathochromic shift and broadening of the emission peak when compared to the solution photoluminescence spectrum. The anthracene derivatives with no electronic interactions, as determined by single-crystal X-ray crystallography, produced devices that showed no bathochromic shift and better efficiencies.