Enabling efficient electron injection in stretchable OLED

Stretchable organic light-emitting diodes (OLEDs) are transforming human-machine interfaces and wearable technologies; still, their performance is considerably inferior to commercial, non-stretchable OLEDs, mainly limited by inefficient electron injection. We address this by redesigning both the electron transport layer and the cathode. For the former, we design a copolymer structure with high stretchability and ideal energy levels, achieving performance comparable with standard small-molecule electron transport layers. For the latter, we leverage the liquid metals embrittlement effect to confer stretchability to aluminium thin films, without compromising their electrical and optical characteristics. Combining these designs, we demonstrate fully stretchable OLEDs with a very high external quantum efficiency of 8% and a very low turn-on voltage of 3.5 V, which is on par with the reference rigid OLEDs utilizing the same emitter. This work tackles a crucial bottleneck in stretchable OLED development, bridging the performance gap between stretchable OLEDs and standard rigid OLEDs at the device level, paving the way for high-performance, skin-like displays.