OLED display foils fitted conformally to goggles or cockpit canopies are of considerable interest. As films integrated onto pre-existing lenses or canopies they could provide visual information while adding little weight.
However, the conformal shaping of a displays to its mechanical support causes large deformation strain, in contrast to flexible displays whose bending to cylindrical shape can be managed with little strain. The deformation strain may easily exceed the critical strain of OLED materials, which then rupture and damage or destroy the OLED function. New fabrication techniques and OLED circuit architectures are required to prevent such rupture.
We report an experimental phosphorescent OLED array made on a dome shaped transparent plastic substrate. The pixellated array of OLEDs was fabricated and interconnected while flat. Late in the process sequence the array was shaped to a dome. The OLEDs are protected from rupture by their placement on ITO islands. These ITO islands are sized such that the shear strain developed along them does not reach the critical value. Most of the deformation strain is taken up by the plastic substrate that is exposed between the rigid islands. The metal interconnects do undergo this large deformation and must be designed to withstand it. The substrate was shaped to a dome of 6-cm diameter at its base, with a 10-cm radius of curvature. The radial strain at the apex of the dome is 1.5%.
The process produces bottom emitting phosphorescent OLEDs radiating into the hollow of the dome. OLED yields above 95% were achieved for up to 120-μm islands at area fill factors ranging from 4% to 44%.