Imagine one day rolling your TV screen down like a curtain, or rolling your laptop into a tube for easy storage and transport. It's a vision of a flexible digital display future that Dr. Peyman Servati is helping turn into a reality, and for which he's receiving a 2005 NSERC Doctoral Prize – one of Canada's premier graduate student awards.
"My doctoral research helps pave the way for low-cost, large-area flexible electronics using novel semiconductor materials," says Dr. Servati, a recent Ph.D. recipient in electrical and computer engineering from the University of Waterloo.
The dream of flexible electronic displays comes from the convergence of two technologies over the past 20 years. The first is the ability to print electronic materials, including thin-film transistors, some only tens of nanometres thick, on low cost materials such as plastic – a potentially flexible material.
The second breakthrough was the discovery in 1985 of the organic light-emitting diode (OLED), a carbon-based designer molecule that emits light when an electric current passes through it. OLED displays are brighter and much more power efficient than existing LCD flat panel screens. But their biggest advantage is that they can be printed onto flexible plastic in the same way that an ink-jet printer sprays ink onto a sheet of paper.
The first flat screen OLED monitors are expected out this year. However, when it comes to their flexible future there are some significant technological hurdles. Foremost is that little is known about how to make thin-film transistors and circuits that will hold up under the strains of repeated bending. This bending changes the way electrons flow in the electronic materials and could therefore change the brightness of the display.
In his thesis, Dr. Servati characterized exactly how this electrical behaviour changes under mechanical stress, such as bending. The work was performed in collaboration with Waterloo's Dr. Arokia Nathan, a world-leading large-area electronics researcher.
"Based on these findings, I propose circuits that can function accurately in the presence of the stresses by compensating for the stress-induced changes. My findings can be used to make functional circuits for different flexible electronic applications, including displays," says Dr. Servati, presently a senior research scientist at IGNIS Innovation, Inc. in Waterloo. A spin-off company from the University of Waterloo, IGNIS is working to provide stable circuit solutions for emerging OLED displays.
Dr. Servati's research was the first to create thin-film transistor based circuits that can withstand substrate bending and can compensate for long-term material shortcomings at different operating temperatures.
Dr. Servati believes that the first applications of the flexible displays will be for relatively simple applications, including monochrome displays for flexible e-newspapers or books. But he says the realm of future flexible applications is enormous: "If we integrate thin film transistors with X-ray or light detectors we'll create flexible imagers. These could be very important. For example a doctor could wrap the imager around a patient and get a 3-D image."