Intrinsically stretchable bipolar host with crosslinkable trilayer architecture for high performance full-spectrum...

Developing dedicated intrinsically stretchable host and charge-transport materials to integrate commercial high-performance small-molecule organic emitters into stretchable organic light-emitting diode (OLED) platforms remains a formidable challenge. Herein, we propose a universal cross-linkable trilayer composite film strategy. A series of intrinsically stretchable conjugated polymers based on styrene-reactive cross-linking groups, namely PUCBP, PU2CzSO, and PUBMZ, were designed and synthesized, which respectively impart hole-transport, bipolar host, and electron-transport functionalities, thereby establishing an intrinsically stretchable polymer system for all functional layers. The dense three-dimensional network formed by in situ cross-linking resolves the interlayer intermixing issue inherent in all-solution processing, while the sandwich encapsulation structure effectively suppresses the interlayer migration of small-molecule emitters. This trilayer composite film simultaneously delivers outstanding mechanical and optoelectronic properties, with an elongation at break of 27.91% and a tensile strength of 38.71 MPa, significantly surpassing the comprehensive mechanical performance of single-layer films. Blue, green, and red full-spectrum OLEDs based on this system achieve maximum external quantum efficiencies of 14.52%, 17.32%, and 10.58%, respectively, representing an enhancement of over 60% compared with single-layer devices. Notably, the flexible blue-emitting film attains a maximum luminance of 2391 cd m^-2, retains 95% of its initial luminance after 100 bending cycles at a curvature radius of 5 mm, and maintains 72% of its performance under 20% tensile strain, demonstrating exceptional dynamic deformation stability. This work provides a strategy for the direct application of small-molecule emitters in stretchable composite films and offers a universal, scalable technological platform for the fabrication of full-spectrum, high-efficiency intrinsically stretchable materials.