Foldable organic light-emitting diodes (OLEDs) capable of diverse structural transformations represent one of the most promising candidates for next-generation deformable displays. Controllable folding of flexible OLEDs is a prerequisite for realizing such functions, yet it faces the critical challenge of fabricating pre-programmed folding lines via a solvent-free and non-destructive approach. Here, we report a straightforward method of creating folding lines based on an imprinting process. The folding lines are fabricated by imprinting a transparent film coated on the OLED surface using a PDMS mold. The imprinting process is solvent-free and causes no physical or chemical damage to the functional layers of the OLED. We systematically investigated the effects of the Young’s modulus and thickness of the imprinting layer, as well as the depth of the folding line, on the foldability of the resulting OLEDs. The foldable OLEDs can be sharply folded 180 degrees and transformed into various 3D structures along pre-programmed folding lines. After 1000 times of folding, the device's luminance remains 95% of its initial value. The transparent imprinting layer imposes no restrictions on the light outcoupling direction, enabling the first demonstration of an innovative pattern transformation function based on foldable and transparent OLEDs.
Zhang et al. (Mon,) studied this question.