Use of pi-conjugated organoboron polymers in thin-film organic polymer electronic devices

Abstract

Pi-conjugated organoboron polymers for use in thin-film organic polymer electronic devices. The polymers contain aromatic and or unsaturated repeat units and boron atoms. The vacant p-orbital of the boron atoms conjugate with the pi-conjugated orbital system of the aromatic or unsaturated monomer units extending the pi-conjugation length of the polymer across the boron atoms. The pi-conjugated organoboron polymers are electron-deficient and, therefore, exhibit n-type semiconducting properties, photoluminescence, and electroluminescence. The invention provides thin-film organic polymer electronic devices, such as organic photovoltaic cells (OPVs), organic diodes, organic photodiodes, organic thin-film transistors (TFTs), organic field-effect transistors (OFETs), printable or flexible electronics, such as radio-frequency identification (RFID) tags, electronic papers, and printed circuit elements, organic light-emitting diodes (OLEDs), polymer light-emitting diodes (PLEDs), and energy storage devices employing the pi-conjugated organoboron polymers. In OLED and PLED applications these materials are used as the electron transport layer (ETL) to improve device efficiency. The polymers which exhibit photo- and electroluminescence are also useful as light-emitting material in PLEDs.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0001] This invention was made, at least in part, with funding from National Science Foundation contract DMI-0319320. The United States government has certain rights in the invention.FIELD OF THE INVENTION [0002] This invention relates to the use of pi-conjugated (or π-conjugated) organoboron polymers in thin film electronic devices and methods for the fabrication of such devices. BACKGROUND OF THE INVENTION [0003] The specific functions of many electronic components and devices arise from the unique interactions existing between p-type and n-type conducting and semiconducting materials. Until a few years ago, inorganic conductors and semiconductors entirely dominated the electronic industry. In recent years there has been a major worldwide research effort to develop conducting and semiconducting organic compounds and polymers, and to use them to fabricate plastic electronic devices, such as organic thin film transistor...

AI Technical Summary

Benefits of technology

[0023] Novel polymers of this invention include pi-conjugated organoboron polymers and oligomers that do not contain an aromatic ring in the polymer backbone. However, the novel polymers of this invention may contain one or / more aromatic rings in a side chain, as substituents on the boron atoms or as substituents of the unsaturated carbon atoms of the polymer backbone. The novel polymers of this invention include, among others, poly(vinylborane)s, poly(acetylenylborane)s, poly(divinylborane)s, poly(vinyl acetylenylborane)s, and poly(polyenylborane)s. Representative structures of these novel organoboron polymer compositions useful in the devices of this invention are shown in Scheme 1, formulas a, f and g. More specific structures of novel organoboron polymers of this invention are shown in Scheme 2, formulas D. Representative synthetic methods of these novel polymers are shown in Example 2. Novel polymers of this invention can exhibit improved properties over prior art polymers, particularly those reported by Chujo and coworkers, because the higher density of boron atoms can provide higher electron-deficiency.

[0025] Novel polymers of this invention also include structures E, F, G, H, and I of Scheme 2. Representative synthetic methods of these novel polymers are given in Example 7. These novel polymers can provide improved properties compared to known polymers because of the higher electron deficiency of the aromatic unit.

[0026] Methods or improved methods for synthesis of certain pi-conjugated organoboron polymers are also provided. A significant improvement of the method of preparation of poly(arylborane)s polymers 3a-3e over prior art methods is the use of an organolithium derivative rather than a Grignard reagent and the use of cyclohexane (a cyclic hydrocarbon) rather than tetrahydrofurane (THF) or other oxygenated solvent. The improved methods provide polymers having boron atoms that are free from coordination, while prior art methods provide polymers having the boron atoms coordinated to the solvent. Coordination with the solvent partially fills the empty p orbital of the boron atoms and decreases the electron-deficiency of the polymer.

Problems solved by technology

Some ICPs function as semiconducting polymers in their undoped state, however other ICPs are not stable in their semiconducting state.

In contrast, it is more difficult to design electron-deficient conjugated polymer systems.

Unfortunately, current n-type semiconducting polymers have generally poor properties, including low charge carrier density and low carrier mobility.

Furthermore, most of these materials are difficult to process, and some of them are difficult to synthesize.

The disadvantage of these non-polymeric semiconducting species is the low charge carrier mobility due to the limited conjugation (due to low molecular weight), and the fact that they often need to be processed by vacuum deposition techniques.

Marder et al. reports that three-coordinate boron species are equivalent to carbonium ions, and are thus extremely electron-deficient systems.

The n-type semiconducting properties and photoluminescence of these materials have been reported, but the materials were not shown to be useful in thin film, organic polymer electronic devices, such as OPVs (organic photovoltaics), PLEDs, or OFETs.

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