Host-guest design for stretchable light-emitting polymers reaching an EQE of 20%

Stretchable light-emitting devices are poised to play a central role in advancing human–technology integration, enabling applications such as on-skin displays, optical sensing, and implantable phototherapy. Among them, stretchable organic light-emitting diodes (OLEDs) are particularly attractive due to their high efficiency and potential biocompatibility. The recent realization of thermally activated delayed fluorescence (TADF) in stretchable emitters, enabling triplet exciton harvesting, has increased external quantum efficiency (EQE) to 10%. However, triplet–triplet annihilation (TTA) remains a key barrier to further improvement toward commercial-grade performance. Here, we introduce a stretchable host–guest emitter design that overcomes this quenching mechanism by uniformly dispersing TADF small-molecule guests within a newly designed stretchable host polymer. This architecture enables efficient exciton transfer while suppressing TTA, yielding an external quantum efficiency (EQE) of 20.3%—doubling the performance of prior state-of-the-art. Notably, the guest molecules also act as plasticizers, enhancing stretchability beyond 150%. With generalizability to different TADF emitters, this work establishes a foundational strategy for mitigating TTA in stretchable emissive layers, advancing soft optoelectronics toward commercial viability with mechanical durability and practicality.