The project explored the low temperature, maskless digital fabrication of organic thin-film transistors (OTFTs) on large area rigid and flexible substrates used in flexible display backplanes.

During the manufacturing of OTFT backplanes, defects can occur at a number of different stages, caused by anomalies such as contamination and thickness variations in the conductive and semi conductive layers. Defects are highly detrimental to the performance of the backplanes.

For the mass market adoption of flexible displays used in future consumer devices such as bendy smartwatch displays and foldable mobile phones, there is a need throughout the industry to detect backplane defects at high speed and using roll-to-roll manufacturing techniques. To do this, specialist high speed and high resolution systems are needed. The aim of DigiPRINT was to develop the technologies and software needed for the in-line detection and repair of micro and nano-scale defects on backplanes, at proof of concept scale.

Project Achievements

• Large area high resolution (<10μm) printing by laser-assisted IJ and LIFT of functional OTFT materials
• Low leakage fast switching OTFT by laser direct-write selective layer nano-patterning (10⁶ on/​off ratio at high mobility)
• High resolution defect repair of (mis)printed lines (10μm) by digital laser transfer combining LIFT and laser sintering
• Non-contact surface metrology tools for online quality control suitable for high volume roll-to-roll processing.

During the project both laser-assisted inkjet printing and laser-induced forward transfer of functional materials were investigated. The project developed industrial, ultra-fast DPSS lasers with non-contact optical metrology heads for real-time monitoring of deposition and patterning processes.

Further development work will be carried out by CPI to assess the economic feasibility of these technologies, by providing the expertise and capability to test and develop the technologies from batch processes through to roll to roll processes at pilot production scale.