Interfacial dipole-engineered fiber optoelectronic devices with enhanced efficiency and stability

Organic light-emitting diodes (OLEDs) have been developed to enhance device lifetime, efficiency, and operational stability. However, the widely used hole injection layer (HIL) material poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) exhibits limitations such as high work function and acidity, which degrade device performance. This study introduces a [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) self-assembled monolayer (SAM) as an alternative to PEDOT:PSS. 2PACz-based OLEDs achieved lower turn-on voltages and higher external quantum efficiencies (EQEs) compared with PEDOT:PSS-based devices. The maximum EQE of green and red fiber organic light emitting diodes (FOLEDs) were 10.71% and 8.97%, respectively, representing 16.9% and 12.9% improvements compared with those of reference devices using PEDOT:PSS as the HIL. Furthermore, compared with TiO₂ fiber-shaped dye-sensitized solar cells (FS-DSSCs), the incorporation of TiO₂/2PACz increased the power conversion efficiency (PCE) from 5.67% to 6.53%, corresponding to an improvement of approximately 17%. Notably, the TiO₂/2PACz-based fiber-shaped gas sensors (FS-GSs) also exhibited enhanced gas sensing characteristics, including increased response and sensitivity, highlighting the multifunctionality and broad applicability of this interfacial engineering strategy across diverse optoelectronic platforms.