Organic-Passivated ZnON TFTs with Extended Lifespan for OLED Driving

Amorphous zinc oxynitride (a-ZnON) has emerged as a promising channel material for thin-film transistors (TFTs) used in active-matrix organic light-emitting diode (AMOLED) backplanes due to its high electron mobility and improved bias stability compared to conventional zinc oxide (ZnO). However, the weak Zn−N bonding nature of ZnON inevitably leads to nitrogen volatilization under ambient conditions, resulting in severe threshold voltage instability and limited device lifetime. Here, we demonstrate a simple, reproducible, and effective strategy for suppressing nitrogen loss in ZnON TFTs using spin-coated organic passivation layers. Among the investigated materials, SU-8 provides exceptional environmental protection, enabling ZnON TFTs to maintain stable electrical characteristics over 20 weeks under ambient storage conditions. The SU-8-passivated devices exhibit a minimal threshold voltage shift (∼2 V), high field-effect mobility (16 cm 2 V −1 s −1 ), an on/off current ratio exceeding 1.6 × 10 8, and the smallest hysteresis variation over time among the investigated passivation materials. The superior performance is attributed to the dense molecular structure, low moisture permeability, and excellent surface planarization of the SU-8 layer, as verified by calcium tests, atomic force microscopy (AFM) analysis, and bias-stress measurements. These results establish organic SU-8 passivation as a practical and scalable approach for realizing long-lived, high-performance ZnON TFTs, highlighting their strong potential for next-generation AMOLED backplane applications.