title: High rectification in organic diodes based on liquid crystalline phthalocyanines.
abstract: The optical and electrical properties of mesogenic metal-free and metalated phthalocyanines (PCs) with a moderately sized and regioregular alkyl periphery were investigated. In solution, the individualized molecules show fluorescence lifetimes of 4-6 ns in THF. When deposited as solid thin films the materials exhibit significantly shorter fluorescence lifetimes with bi-exponential decay (1.4-1.8 ns; 0.2-0.4 ns) that testify to the formation of aggregates viaπ-π intermolecular interactions. In diode structures, their pronounced columnar order outbalances the unfavorable planar alignment and leads to excellent rectification behavior. Field-dependent charge carrier mobilities are obtained from the J-V curves in the trap-limited space-charge-limited current regime and demonstrate that the metalated PCs display an improved electrical response with respect to the metal-free homologue. The excited-state lifetime characterization suggest that the π-π intermolecular interactions are stronger for the metal-free PC, confirming that the metallic centre plays an important role in the charge transport inside these materials.
authors.affiliation: Centre de Recherche Paul Pascal, Université de Bordeaux & CNRS, 115 Avenue Schweitzer, 33600 Pessac, France.
authors.forename: Petru
authors.initials: P
authors.lastname: Apostol
authors.forename: Juliana
authors.initials: J
authors.lastname: Eccher
authors.forename: Marta Elisa Rosso
authors.initials: ME
authors.lastname: Dotto
authors.forename: Cassiano Batesttin
authors.initials: CB
authors.lastname: Costa
authors.forename: Thiago
authors.initials: T
authors.lastname: Cazati
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Hillard
authors.forename: Harald
authors.initials: H
authors.lastname: Bock
authors.forename: Ivan H
authors.initials: IH
authors.lastname: Bechtold