Organic Power Devices in Mains-Powered Converter

March 22, 2017 by Jeff Shepard

Organic light-emitting devices and printed electronics can be connected to a socket in the wall by way of a small, inexpensive organic converter, developed in a collaboration between Linköping University and Umeå University. The organic ac-dc converter consists of diode-connected organic thin-film transistors, operated at high voltages up to 325V.

“In our prototype design, we present a current supply, comprising a single organic thin-film transistor (OTFT), for the charging of supercapacitors. The current supply takes power from the electric grid (115Vac, the US standard), converts the ac voltage to a quasi-constant dc current of about 0.1 mA regardless of the impedance of the load. The output is used to charge a supercapacitor,” stated Deyu Tu.

“Solution-processed OTFTs based on the popular polymeric semiconductor poly(3-hexylthiophene-2,5-diyl) have been developed to rectify the 115Vac. A diode-configured OTFT was used as a half-wave rectifier. The single OTFT current supply was demonstrated to charge a 220mF supercapacitor to 1V directly using 115Vac as the input. This work paves the road towards all-printable supercapacitor energy-storage systems with integrated chargers, which enable direct charging from a power outlet,” Deyu Tu continued.

Printed electronics and organic light-emitting devices now perform at levels sufficient for a number of eco-friendly, energy-efficient applications. Previously the idea has been to drive the organic electronics using solar cells, batteries or wireless transformers, which works well in many cases. But for fixed installations like lighting, signage or UV-blocking windows, it is convenient to use a wall socket. Until now this has not been possible, because the high voltage damages the electronics.

2017 Docent Deyu Tu from LiU’s Division of Information Coding has led a project where colleagues at Umeå University joined forces to find a solution to this problem. And they have now been able to demonstrate an organic converter that makes it possible to drive organic light-emitting devices with high luminescence, and to charge supercapacitors, both using electricity from an ordinary wall socket.

“For the first time in the world we have been able to demonstrate an ac-dc converter in organic electronics that functions at voltages above 300V,” says Deyu Tu.

“Our converter paves the way for a wave of flexible, thin, cost-effective and eco-friendly solutions for the electronics of the future.”

This is a pioneer work of organic ac-dc converters, a first stage to prove the concept of organic power electronics. To be used in real products, the power conversion efficiency needs to be improved.

”We have initiated the follow-up work to deal with this issue”, says Deyu Tu.

The results have been published in two journals – Organic Electronics and ECS Transactions – and have generated so much interest that Deyu Tu has been invited to speak at major conferences in China and Japan. The project has received financial support from the Swedish Foundation for Strategic Research.