High-efficiency stretchable organic light-emitting diodes based on ultra-flexible printed embedded metal composite electrodes

Stretchable organic light-emitting diodes (OLEDs) are important components for flexible/wearable electronics. However, the efficiency of the existing stretchable OLEDs is still much lower as compared with their rigid counterparts, one of the main reasons being the lack of ideal flexible transparent electrodes. Herein, we propose and develop a printed embedded metal composite electrode (PEMCE) strategy that enables the fabrication of ultra-thin, highly flexible transparent electrodes with robust mechanical properties. With the flexible transparent electrodes serves as the anodes, flexible/stretchable white OLEDs have been successfully constructed, achieving a current efficiency of up to 77.4 cd A(-1) and a maximum luminance of 34 787 cd m(-2). The current efficiency of the resulting stretchable OLEDs is the highest ever reported for flexible/stretchable white OLEDs, which is about 1.2 times higher than that of the reference rigid devices based on ITO/glass electrodes. The excellent optoelectronic properties of the printed embedded transparent electrodes and the light extraction effect of the Ag-mesh account for the significant increase in current efficiency. Remarkably, the electroluminescence performance still retains similar to 83% of the original luminance even after bending the device 2000 cycles at a radii of similar to 0.5 mm. More importantly, the device can withstand tensile strains of up to similar to 100%, and even mechanical deformation of 90% tensile strain does not result in a significant loss of electroluminescence performance with current efficiency and luminance maintained at over 85%. The results confirm that the PEMCE strategy is effective for constructing ultra-flexible transparent electrodes, showing great promise for use in a variety of flexible/stretchable electronics.