Highly Efficient Intrinsically Stretchable OLEDs from Thermally Activated Delayed Fluorescence

Light-emitting devices are crucial for human-machine interfaces, which would function as read out displaying platform, health sensors, therapy unit, or optical neurostimulator in optogenetics. Considering the operation scenario of these devices, mechanical stretchability and electroluminance (EL) performance are two of the key aspects of device design. To achieve stretchability, we have reported a feasible method that is copolymerizing soft chain with conjugated functional unit. To achieve decent EL performance, among current light-emitting technologies, organic light-emitting diodes (OLEDs) stand out for their high efficiency, brightness, and low working voltage. To the best of our knowledge, most of the reported stretchable OLED are based on fluorescence emitters, 1^st generation of OLED emitter. This kind of emitter has relatively simple requirements since it only harvest its singlet excitons, which leads to a theoretical internal quantum efficiency (IQE) as 25%. In contrast, thermally activated delayed fluorescence (TADF) emitters, the 3^rd generation of OLED emitters, are more preferred due to its organic constituents as well as a near-unit IQE. However, its complicated device structure and requirement of energy alignment make the realizing of highly efficient fully stretchable TADF devices very challenging. Here, we want to bring up with a fully stretchable OLED devices based on TADF mechanism reaching an external quantum efficiency (EQE) around 20% and crack-onset strain exceeding 120%.