The researchers in organic electronics have a favourite material to work with: the conducting polymer PEDOT:PSS, which conducts both electrons and ions. Displays and transistors manufactured from this polymer have many advantages, which include that they are simple and cheap to manufacture, and the material itself is non-hazardous. It has, however, been difficult to create devices that switch rapidly at a specific voltage, known as the 鈥渢hreshold voltage鈥�. This gives that it has, so far, been difficult to control the current state of the transistors or the color state of the displays in a precise manner.
鈥淭he lack of any threshold in the redox-switching characteristics of PEDOT:PSS hampers bistability and rectification, characteristics that would allow for passive matrix addressing in display or memory functionality鈥� says Simone Fabiano, senior lecturer at the Laboratory of Organic Electronics, LOE, who is the principal author of the article in Science Advances, together with Negar Sani from the research institute RISE Acreo.
Head of the laboratory Professor Magnus Berggren couldn鈥檛 let this idea rest, and when he was awarded a research grant from the Knut and Alice Wallenberg Foundation in December 2012 to use freely, this was one of the high-risk projects he chose to invest in.
鈥淲e called the research then breakneck research, and here is a result. Our demonstration proves that truly leading research typically take a long time and require considerable patience. Simone Fabiano has done tremendous work here, and refused to give up when others have doubted,鈥� says Magnus Berggren.
鈥淭he thickness of the layer determines the voltage at which the circuit switches or the display changes colour. Transistors are no longer required in the displays: we can control them pixel-by-pixel simply through a thin ferroelectric layer on the electrode,鈥� says Simone Fabiano.
The LOE research group shows in the article that 鈥渇erroelectrochemistry鈥�, the combination of ferroelectricity and electrochemistry, can be used in displays in the field of printed electronics and in organic transistors. The scientists envisage, however, many other areas of application.
鈥淔erroelectrochemical components can easily be integrated into memory matrices and into bioelectronic applications, just to give a couple of examples,鈥� says Simone Fabiano.
鈥淭he field of ferroelectrochemistry doesn鈥檛 actually exist, but we have achieved success using this combination,鈥� Magnus Berggren concludes.
The research has later also received funding also from the Swedish Foundation for Strategic Research, SSF, and Vinnova.
The article: 鈥淔erroelectric polarization induces electronic nonlinearity in ion-doped conducting polymers,鈥� Simone Fabiano, Negar Sani, Jun Kawahara, Lo茂g Kergoat, Josefin Nissa, Isak Engquist, Xavier Crispin and Magnus Berggren, Laboratory of Organic Electronics, Department of Science and Technology, Link枚ping University, Campus Norrk枚ping. Science Advances 2017. DOI 10.1126/sciadv.1700345
鈥淭he lack of any threshold in the redox-switching characteristics of PEDOT:PSS hampers bistability and rectification, characteristics that would allow for passive matrix addressing in display or memory functionality鈥� says Simone Fabiano, senior lecturer at the Laboratory of Organic Electronics, LOE, who is the principal author of the article in Science Advances, together with Negar Sani from the research institute RISE Acreo.
Wild ideas
More than five years ago a wild idea arose at the Laboratory of Organic Electronics: could you solve this problem by combining electrochemistry with ferroelectricity? Ferroelectric materials consist of dipoles. One end of a dipole has a positive charge and the other a negative charge, and these 鈥渇erroelectric鈥� dipoles rotate when they are exposed to an electric field beyond a specific threshold.Head of the laboratory Professor Magnus Berggren couldn鈥檛 let this idea rest, and when he was awarded a research grant from the Knut and Alice Wallenberg Foundation in December 2012 to use freely, this was one of the high-risk projects he chose to invest in.
鈥淲e called the research then breakneck research, and here is a result. Our demonstration proves that truly leading research typically take a long time and require considerable patience. Simone Fabiano has done tremendous work here, and refused to give up when others have doubted,鈥� says Magnus Berggren.
Ferroelectric material
After many years of tenacious experiments, Simone Fabiano and his colleagues at the Laboratory of Organic Electronics have managed to apply a thin layer of a ferroelectric material onto one electrode in organic electrochemical devices and circuits.鈥淭he thickness of the layer determines the voltage at which the circuit switches or the display changes colour. Transistors are no longer required in the displays: we can control them pixel-by-pixel simply through a thin ferroelectric layer on the electrode,鈥� says Simone Fabiano.
The LOE research group shows in the article that 鈥渇erroelectrochemistry鈥�, the combination of ferroelectricity and electrochemistry, can be used in displays in the field of printed electronics and in organic transistors. The scientists envisage, however, many other areas of application.
鈥淔erroelectrochemical components can easily be integrated into memory matrices and into bioelectronic applications, just to give a couple of examples,鈥� says Simone Fabiano.
Ferroelectrochemistry
The technology is now protected by patents.鈥淭he field of ferroelectrochemistry doesn鈥檛 actually exist, but we have achieved success using this combination,鈥� Magnus Berggren concludes.
The research has later also received funding also from the Swedish Foundation for Strategic Research, SSF, and Vinnova.
The article: 鈥淔erroelectric polarization induces electronic nonlinearity in ion-doped conducting polymers,鈥� Simone Fabiano, Negar Sani, Jun Kawahara, Lo茂g Kergoat, Josefin Nissa, Isak Engquist, Xavier Crispin and Magnus Berggren, Laboratory of Organic Electronics, Department of Science and Technology, Link枚ping University, Campus Norrk枚ping. Science Advances 2017. DOI 10.1126/sciadv.1700345
