24-08-2020 | By Sam Brown
Researchers are exploring the use of Diketopyrrolopyrrole dye, better known as the pigment used in Ferrari Red, to fabricate low-cost organic electronics. What are OFETs, what advantages do organic electronics have, and what applications may they find themselves in?
Diketopyrrolopyrrole dye, also known as DPP, are a range of organic dyes and pigments that utilise dilactam 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione. While their name and chemical composition are rather complicated, their usage in paints is very simple. Due to their resistance to photodegradation (i.e. ability to resist ageing in the presence of light), they are often used in the automobile industry. One typical example of where DPPs can be found is the dye responsible for the Ferrari Red colour. However, DPPs have more applications than just paint; their ability to work as fluorescence makes them a candidate for bioimaging applications.
The ability for DPP to carry charge has led to investigations into DPP, and what it may be capable of doing. For example, DPP has been used in carbon-based semiconductors for use in printable and wearable organic electronic devices. Now, a team of researchers have combined DPP with naphthalene, an organic hydrocarbon, to produce a semiconductor capable of producing solar cells, transistors, and circuits. What makes the research into the DPP / Naphthalene semiconductor critical is the significant price drop. Currently, crystalline solar cells (perovskite) utilise a chemical element called Spiro-OMeTAD, that results in a final cost of approximately $1000 per gram. However, the new semiconductor material based on DPP results in $200 per gram, 5 times saving. It is hoped that the introduction of DPP semiconductors will encourage further development in organic electronics technology, and eventually bring organic solutions to the market.
OFET is an acronym for Organic Field-Effect Transistor, and as the name suggests, are field-effect transistors which utilise organic semiconductors. OFETs are very similar to Thin Film Transistors (TFTs), and as such can often be found in similar applications including flexible displays and printed electronics. While OFETs can be created using vacuum deposition, they can also be constructed using low-cost methods, including inkjet printing and solution-casting.
Organic electronics, being based on organic compounds, have the advantage of being biodegradable and thus have a lower impact on the environment when compared to their silicon counterparts (however, this does not consider the environmental impact of manufacturing). Another significant advantage of organic electronics over other thin-film technologies is their superior flexibility, and this has been demonstrated with the development of displays that can be rolled up without breaking. Organic electronics can also be used to create most, if not all, components including resistors, capacitors, sensors, transistors, and LEDs. This means that a circuit, in theory, can be built using the same technology, and this provides potential advantages in ease of manufacturing (i.e. fabricate entire products in a single step).
The combination of their flexibility and printability makes organic electronics a strong candidate for future wearable electronics. One of the most significant issues currently faced by wearable electronics is the inherent rigidity of electronics (such as semiconductors). Still, an organic-based system could provide designs that mould themselves to the wearer. The ability to be printed to flexible materials also leads to the possibility that organic electronics could be applied directly to human skin. Since organic electronics components can be made into many different types of sensors (including temperature, moisture, and strain gauges), a custom biometric system could be quickly applied to a user’s skin. Power could easily be applied with the use of NFC technology, whereby a power transmitter is worn in a pocket, and an NFC inductor coil could be printed on the side of the leg/hip where the power unit is placed.
The flexibility of organic electronics will also find themselves useful in flexible display applications. While not currently commercialised, flexible OFET-based displays have already been produced and shown to work with the ability to display both full colour and work at nominal video refresh rates. These displays would find themselves useful in a range of modern applications, including foldable smartphones, curved screens, and wearable interfaces.
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