Ultra-flexible, high-performing NAN transparent electrodes for bendable optoelectronic applications

The NiO/Ag/NiO (NAN) structure, a member of the oxide/metal/oxide (OMO) structures, was developed as an alternative to conventional transparent electrodes. The fabrication process employed combination of RF-magnetron sputter and e-beam evaporation techniques, and to optimize the electrode performance, the Ag layer thickness within the NAN structures was varied between 4 and 20 nm. The resulting configurations were evaluated through the Fraser-Cook and Haacke figures of merit (FoM). The optimized structure exhibited high optical transmittance of 75% and a low sheet resistance (RS) of ∼5 Ω/□. Compared to a commercial sample of indium tin oxide (ITO) coated polyethylene terephthalate (PET), the NAN/PET structures show higher Fraser-Cook FoM, closely aligned with the Haacke FoM, owing to their lower RS values. In addition, the flexural resistance of the electrodes was assessed by subjecting the samples to 10,000 bending cycles. Following this test, the RS value of ITO/PET increased 26.3 times to 3312.89 Ω/□, while the NAN/PET only increased 1.25 times to 7.82 Ω/□. Even the least performing NAN sample, deposited on polyethylene naphthalate (NAN/PEN), experienced a moderate increase in resistance, stabilizing at 59.93 Ω/□. The obtained results highlight the great potential of the NAN structure as an electrode for flexible optoelectronic devices.