The researchers have developed a new process for this purpose: Small molecules are combined to form polymers that can transport negative charge carriers (electrons). The highlight is that, unlike comparable polymers, this polymer is in the liquid state. This enables them to print or spray very thin and smooth organic functional layers on surfaces.
The researchers now want to develop thermoelectric generators that supply energy to sensors in places that are difficult to access, for example, where battery replacement is not useful, not possible or very expensive. In particular, the researchers think about warm pipes that do not get hotter than 100 degrees Celsius – which is the upper limit for the polymers investigated so far. There are plenty of applications on the Internet of Things: sensors and electronic devices could use these thermoelectric generators to cover their own electrical energy requirements.
Thermoelectric generators have been known as a concept for years. However, their efficiency is still far too low for mass use: on average, they convert only 6% of thermal energy into electrical energy. However, if it were possible to significantly increase the yield, this could have far-reaching consequences for energy balances: Car manufacturers, for example, have long dreamed of coating their engines with such thermoelectric generators in order to electrically recycle the waste heat from the drive units, which had previously been painstakingly cooled away.
According to estimates, the fuel consumption of cars could be reduced by up to a tenth. However, the solutions tested to date are not very effective.
With the polymer technology from the Fraunhofer IWS, this could change in the future. The researchers from Dresden have taken an important step: they have found a way to liquefy polymers of the n-type and then process them further. What’s important here is that your polymer layers remain comparatively stable under everyday conditions. This is not something that can be taken for granted. Such long organic molecules tend to age and lose their special properties when they come into contact with air.
IWS researchers Roman Tkachov and Lukas Stepien have developed a multi-stage process to produce their inks on the basis of conductive polymers. This allows high-quality, smooth layer structures that – depending on the process – are only one tenth to ten micrometers thick. This in turn allows for more compact and effective components than the polymers previously used. The researchers also see considerable potential for their technology in the construction of organic transistors and solar cells. Until then, however, some research work still needs to be done.
Initially, the engineers will concentrate on further increasing the electrical conductivity of their polymers. They also want to produce the first prototypes of thermoelectric generators from their new materials. In addition, their next efforts will focus on increasing efficiency.