Achieving Near Unity Photoluminescence Quantum Yield and High Stretchability in TADF Polymers with Small Molecule Plasticizer Blending

Stretchable light-emitting polymers serve as key components for skin-like displays and optical bio-stimulations. In the development, it is crucial to enhance both luminescence efficiency and mechanical stretchability. While "first-generation" organic emitters can only harness singlet excitons with a theoretical quantum yield of 25%, "third-generation" organic emitters can harness triplet excitons through thermally activated delayed fluorescence (TADF), achieving a theoretical near-unity photoluminescence quantum yield (PLQY). However, in polymer systems, it remains challenging to achieve near-unity PLQY, while stretchability is lacking in most of the reported TADF polymers. In this talk, we will present a method of blending small molecule plasticizers into TADF polymers to both enhance luminescence efficiency and increase stretchability. For the luminescence property, this method gives universal enhancement of PLQY of all tested TADF polymers by as high as 165%, thereby achieving near-unity photoluminescence quantum yield (PLQY) of 98.7%. For mechanical properties, stretchability up to 150% strain can be obtained. Demonstrated in organic light-emitting diodes (OLEDs), the TADF-plasticizer system underscores the potential to improve both the optical and mechanical properties of TADF-based stretchable devices, paving the way for highly efficient, bright, and mechanically robust stretchable optoelectronics.