Wide Band Gap Polymer Network for Blue OLED and Self-Biased High-Sensitivity UV Photodetector

In this study, we report the synthesis of a wide band gap, solution-processable conjugated polymer network (CPN), TBOB, incorporating triazine and bis(octyloxy)benzene units in a donor–acceptor architecture for multifunctional use in blue organic light-emitting diodes (OLEDs) and self-biased UV photodetectors. Comprehensive thermal, photophysical, and electrochemical analyses show that TBOB possesses excellent thermal stability (glass transition temperature, Tg ≈ 117 °C), strong UV absorption, bright fluorescence with a high quantum yield (Φ = 0.82), and a wide band gap of 2.7 eV. OLEDs fabricated with TBOB as the emissive layer exhibit blue emission with CIE coordinates of (0.17, 0.19), a maximum external quantum efficiency of 2.8%, a peak brightness of 5273 cd/m2, and a current efficiency of 2.8 cd/A. In addition, a planar heterojunction UV photodetector was constructed using ZnO as the electron-transporting layer and TBOB as the photoactive material. The device demonstrates high responsivity (4.47 AW–1) and detectivity (2.9 × 1011 Jones) at −5 V under 370 nm illumination. Notably, the photodetector shows stable, fast (rise time: 23 ms; fall time: 32 ms), and reproducible photoresponses, along with a high dark-to-light current ratio (∼162 at 10 μW cm–2) under zero bias, confirming its self-powered operation. Overall, these findings highlight the strong potential of TBOB-based conjugated polymer networks for dual applications in the fields of optical illumination (OLEDs) and UV photodetectors.