A Universal Cathode Lamination Protocol for Intrinsically Stretchable Light-Emitting Didoes

Soft material and processing techniques have enabled the development of a variety of wearable electronics which requires the devices to be stretchable to form a conformal contact on human skin. However, the development of the stretchable display is greatly stagnant due to the lack of a protocol for the deposition of stretchable cathode materials. Alternatively, a direct solution process on the light-emitting layer will deteriorate the device's stability. In addition, conventional physical vapor deposition of rigid metal electrodes is not applicable for stretchable applications. Hence, the electrode materials that can be used as the cathode is greatly limited. In this research, we have developed a universal cathode lamination protocol with the aid of solvent annealing and hot pressing. The quality of the lamination is evaluated using the image-assisted analysis method and photoluminescence. Based on this lamination protocol, we have developed intrinsically stretchable light-emitting diodes (ISLED) with a turn-on voltage of lower than 4 V and maximum luminance over 1700 cd/m², indicating a well-contacted cathode-emitting layer interface. Furthermore, a three-inch five-by-five matrix has been successfully demonstrated with the application of tensile strain using the convex stretching method. This work could provide a guideline for developing an ISLED and stimulate considerable research on fundamental aspects of ISLEDs and furthermore into practical applications in both academia and industries.