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The fields of organic electronics and nanoelectronics have been undergoing significant advancements in recent years as scientists seek to miniaturize electronic devices via a number of routes. Polymers offer a way of miniaturizing certain elements of an electronic device and interesting ways of integrating nanoelectronics onto different surfaces.
Many would not think of polymers as a useful material for electronics and nanoelectronics since most of them are dielectric (insulating) in nature. However, there are those that are conductive in nature, and the ability for them to be synthesized in small sizes, as well in different architectures and mediums, has meant that their use has been growing across a number of electronic devices.
Moreover, some polymers which are dielectric in nature still have a place in nanoelectronic devices for housing more active materials, either as a composite within the device or as an active coating.
The Field of Nanoelectronics
Nanoelectronics is an area where conventional electronics and nanotechnology meet. The field has been governed by a drive to make devices smaller while ensuring that their efficiencies remain at least the same, if not better.
Nanoelectronics has significantly grown in the last couple of decades because of methods of producing nanomaterials, i.e. bottom-up nanofabrication methods, have significantly advanced, as have nanomaterial incorporation and characterization methods.
Nanoelectronic devices come in many forms and there are a large number of different nanomaterials, nanostructured materials and nanoforms of bulk materials that can now be used to effectively construct these devices. The future of electronic devices will be heavily reliant on creating efficient nanoelectronic devices.
Combining Polymers with Nanoelectronics
Polymers are chiefly used as a host matrix for nanomaterials so that they can be used in a functional way. These are usually in the form of a coating or composite, although there are instances where polymers can be used on their own. Because polymers are inherently flexible, behave as a strong and stable host for other materials, and in some instances can be conductive, they are a material that is well-positioned for certain electronic devices, namely flexible, wearable and transparent electronics and nanoelectronics.
Their ease of processing and ability, self-assembly processes, and ability to be made at the nanoscale enables them to be incorporated in a wide range of organic nanoelectronic devices, such as some semiconductor junctions, organic transistors, organic solar cells, biosensors, and various other thin-film electronics.
So, while they may not be the most obvious or traditional material, they can certainly push the boundaries of modern electronics and nanoelectronics, and be used to create and incorporate nanoelectronic devices in a different manner to many other materials.
Aside from being used to create nanoelectronic devices, polymers are also a common choice for coating such devices to protect them from environmental stimuli and to dissipate internal heat.
Examples of Where Polymers Can Be Used
There are far too many examples where polymers can be integrated with nanomaterials, or used on their own, to showcase in detail. Below are some examples; one where polymers have shown promise on their own recently (single molecule device) and in emerging fields where polymers are combined with more active nanomaterials (nanosensors and solar cells).
While solar cells themselves are not nanoelectronic devices, a lot of the components in the cutting-edge solar cells utilize nanomaterials, or nanosized components. Moreover, nanostructured polymers have been used with flexible organic solar cells, transparent solar cells, and dye-sensitized solar cells.
While they can be used within different aspects of these solar cell devices, some of the most common uses include hole transfer materials and electron transfer materials, as well as the interface layer, donor layer, or buffer layer. The use of polymers in solar cells typically enables the complete device to be more flexible and they are a key component of many of the flexible and thin-film solar cells that are now emerging.
Polymers have made a lot of nanosensors possible, especially those embedded into thin coatings. The use of polymers in nanosensors is mostly centered around the polymers taking a more passive role, rather than being the active sensing medium. However, this is something that works very well for some applications, such as food packaging sensors.
For example, these types of sensors are usually nanoparticles/nanosheets that emit a color change when sensing, so the ability to host such small ‘sensor nanoparticles’ is advantageous as it keeps the cost down and the application of the coating is easy.
There are also a range of nanosensors across the medical space which use polymers as the host/structural medium and employ a nanoarchitectured material/nanomaterial as the active sensing material.
There are also some sensors in the biomedical space which use the different forms and architectures that polymers can exhibit in the form of all-polymer nanosensors, and these are particularly useful for investigating complex biostructures such as biological membranes, as well as changes in biological environments.
So, while polymers don’t play the most active role in nanosensors, their inclusion is vital for the commercial realization for some applications due to economic, ease of processing, long-term stability and performance reasons.
It’s emerged recently that some polymers could become a useful material for single-molecule electronics. It is only early days, but nanoscale polymers have been probed with a scanning tunneling microscope (STM). This approach created an electronic junction between the tip of the STM and the polymer, so that a current can flow into the polymer. This enabled the researchers to determine the suitability for some polymers to be used in single-molecule electronics.
The researchers investigated the suitability of poly(vinylpyridine) (PVP), and found that it could form a stable electronic junction and that a polymer junction was much more stable than a junction composed of its monomer counterpart. The current flowing through the polymer was found to be stable with minimal deviations.
So, while it’s early-stage research, it showcases the possibility that the area of polymer nanoelectronics could continue to expand and it shows that polymers themselves are a suitable material for nanoelectronic devices.
References and Further Reading