Flexible displays for the future

The Centre for Process Innovation (CPI) has made significant progress towards the development of flexible displays and screens, with a novel process for the fabrication of bendable Organic Thin Film Transistor (OTFT) arrays.

The process allows the arrays of OTFTs, which operate the pixels in a screen, to be bent to a radius of 1mm without a significant reduction in device performance. This has helped to advance the suitability of OTFT arrays for integration into backplanes, the ​‘circuit boards’ for displays found in such devices as mobile phones or digital cameras, for the eventual production of ultra-flexible, active-matrix organic light emitting diode (AMOLED) displays.

In the future, such technology could not only allow the production of roll-up televisions or mobile phones, but the fabrication of displays on thin flexible surfaces could be used to create paper like documents such as animated newspapers or magazines.

Whilst previous research has tended to examine large OTFTs, CPI fabricated and tested OTFTs at 10 microns, a similar size to those found in current displays, mechanically bending the backplane to which they were applied, over 10,000 times in four hours.

A demonstration video of the bend testing of the array can be viewed here.

In order for CPI’s OTFTs to be repeatedly bent to such a small radius, the layers that constituted the backplane were carefully crafted to ensure they remained ​‘stuck’ correctly in place and moved simultaneously under strain, as any independent movement would destroy the device.

Although organic transistors are traditionally quite sensitive to modification, results showed minimal changes in the active voltage and current, which is essential for the continuous operation of pixels in display devices.

Dr Simon Ogier, Research and Development Manager at CPI said: ​“Optimising the processing and performance of OTFT devices in flexible substrates is vital if we are to enable their integration into AMOLED backplanes and manufacture flexible devices that can effectively display moving images.

“This work has brought us one step closer to that goal, but the next challenge will be coupling a flexible backplane with an equally flexible frontplane for a fully flexible display.” It is anticipated that the first flexible plastic-based demonstrator display units using CPI’s OTFT technology will be completed during 2014, as a part of the Technology Strategy Board funded, CPI project ROBOLED.

CPI is the UK’s National Centre for Printable Electronics. Focused on the development, scale-up and commercialisation of printable electronics applications, CPI is equipped with an extensive range of assets specifically chosen and developed to allow clients to understand how their products and processes perform under pilot manufacturing conditions.