Control of Charge Transport in Iridium(III) Complex‐Cored Carbazole Dendrimers by Generation and Structural Modification

Abstract

Here, the charge transporting properties of a family of highly phosphorescent iridium(III) complex‐cored carbazole dendrimers designed to have improved charge transport by incorporating carbazole units into the dendrons are studied. Firstly, the effect of the dendrimer generation and the role of dendron for materials with one dendron per ligand of the core are considered. It is shown, in contrast to previously reported light‐emitting dendrimers, that in this case the carbazolyl‐based dendrons have an active role in charge transport. Next, the effect on the charge transport of attaching two dendrons per ligand to the dendrimer core is explored. In this latter case, for the so called “double dendron” material a highly non‐dispersive charge transport behavior is observed, together with a time‐of‐flight mobility of the order of 10−3 cm2 V−1 s−1. Furthermore the lowest energetic disorder parameter (σ) ever reported for a solution‐processed conjugated organic material is found, σ < 20 meV.

Structural Mimics of Phenyl Pyridine (ppy) – Substituted, Phosphorescent Cyclometalated Homo and Heteroleptic Iridium(III) Complexes for Organic Light Emitting Diodes – An Overview

“…To increase the charge transporting properties Gambino et al ., synthesised the complexes 92–95 (Figure ) by substituting carbazole units into the dendrons . The carbazole units act as efficient charge transport moieties.…”

Carbazole-based polymers as hosts for solution-processed organic light-emitting diodes: Simplicity, efficacy

“…Emission color can also be easily tune by mean of the ligands introduced in the coordination sphere of the metal cation, enabling the emission to range from blue to red [29][30][31][32][33][34][35]. Beyond the simple control of the emission color, the emissive layer of an OLED comprising a triplet emitter cannot be only composed of a neat film of this latter (excepted for the emitters of specific design such as the dendrimers-like complexes) [36,37], but requires the metal complex to be diluted in a material named host to avoid self-quenching of the emitter [38]. To date, the most efficient devices are vacuum-processed and for the reproducibility of the electroluminescence (EL) performances, a precise control of the doping concentration of the injection/transport layers and/or the emissive layer during device fabrication are required.…”

Organic semiconductors for device applications: current trends and future prospects

“…The PAMAM decorated [Ru(bpy) 3 ] + 2 dendrimers exhibited similar trend of mobility reductions with increasing generation number [90]. In contrast, iridium core dendrimers with carbazole in each layer [91] exhibited twofold increase in the mobility from (3-6) × 10 -5 cm 2 /Vs for generation 1 to (7.3-12) × 10 -5 cm 2 /Vs for generation 3. Conjugated polymers have been studied extensively for their applications in flexible electronics [54,59,[92][93][94][95][96][97][98][99] and optoelectronic devices [51,93,100] as reported in the published literature.…”