The performance of ultra thin next-generation flexible display technologies is dependent on the structure of polymer-polymer interfaces. Thanks to neutron reflection, researchers can now examine how fabrication procedures affect interface structure and device performance.
Conjugated polymer field effect transistors (FETs) and light-emitting diodes (LEDs) form the basis of flexible display technologies. Research has shown that thermal processing allows the roughness of the polymer interfaces, found within a particular LED, to be systematically controlled over the range 1nm – 5nm [Higgins et al., Advanced Functional Materials (2009) 19, 157]. By combining neutron reflection with optoelectronic measurements researchers have gained insight into the nature of these interfaces; the enhanced photoluminescence found at rougher interfaces can only be explained if significant molecular-level mixing occurs between the two polymers at the interface.
At ISIS scientists controlled the roughness at a conjugated polymer/insulating polymer interface by varying solvent quality. This allowed researchers to correlate charge mobility in FETs with the competing effects of interfacial roughness and molecular packing with the conjugated polymer layer.
New instruments at the ISIS Second Target Station will help scientists to achieve great resolution at the interface. Plans are in place to conduct further experiments at the Second Target Station, including studies of interfaces found in conjugated polymer solar cells.