Intrinsically stretchable and efficient cross-linked small molecular emitter for flexible organic light-emitting diodes

Due to their rigid and plane conjugated skeletons, small molecular semiconductors always present irreversible brittle properties in the nano-film state, which is not conducive to deformation and operation stability in flexible optoelectronic devices. Herein, we proposed a universal side-chain cross-linkable strategy to construct a dynamic network structure of a small molecular semiconductor (F-3OCm) to improve the deformation tolerance for the fabrication of flexible optoelectronic devices. First, model F-3OCm cross-linked films were obtained by thermal annealing, which presented perfect solvent resistance. Compared to control F-3OEt, F-3OCm cross-linked films displayed viscoelastic behavior with low Young's modulus. Additionally, the tensile fracture rates of F-3OCm cross-linked films are enhanced to similar to 20% without obvious cracks, indicating the excellent intrinsic stretchability with excellent deformation stability. In addition, these stretchable films present not only efficient emission behavior with a PLQY of similar to 50% but also have deep-blue emission with tension-ratio-independent color purity. Finally, flexible organic light-emitting diodes (OLEDs) based on the F-3OCm cross-linked films present excellent deformation stability, associated with their intrinsically stretchabilty. Therefore, the side-chain cross-linkage strategy is a promising approach for designing intrinsically stretchable small molecular semiconductor films for flexible electronics. Due to their rigid and plane conjugated skeletons, small molecular semiconductors always present irreversible brittle properties in the nano-film state, which is not conducive to deformation and operation stability in flexible optoelectronic devices.