Fabrication of nucleation induction layer of self-encapsulated metal anode by an atomic layer half-reaction for enhanced flexible OLEDs

Abstract

Transparent conductive films are important components of organic optoelectronic devices. However, current organic light-emitting devices (OLEDs) used in flexible wearable applications are severely restricted by the fragility and poor conductivity of composing ultra-thin electrodes. In this study, poly(methyl methacrylate) (PMMA)/trimethylaluminum (TMA) was prepared through an atomic layer half-reaction and used as a self-encapsulating nucleation layer. The study suggested coordination between the Au atoms with the functional methyl groups of PMMA/TMA to yield an entire substrate surface. The Au nuclei were evenly and densely distributed on the substrate surface, and island growth of Au film was prevented, leading to good flexibility and photoelectric properties of the Au film deposited on the nucleation layer. For instance, a 7 nm thick layer resulted in a sheet resistance of 18.19 ± 0.44 Ω/◻ at 85.89% transmittance. Furthermore, the use of the as-obtained high-performance electrode in flexible organic optoelectronic devices led to repeated bending over 1000 cycles to a radius of 1 mm without significant reduction in the optoelectronic performances. The nucleation induction layer could also function as a bottom encapsulation with a water vapor transmission rate as low as 2.123 × 10−3 g/cm2/day (60 °C/80% relative humidity). Additionally, the nucleation induction layer exhibited excellent performances in fully transparent devices (75.72% transmittance). In sum, these findings look promising for future flexible wearable applications.