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 (R_S) 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 R_S values. In addition, the flexural resistance of the electrodes was assessed by subjecting the samples to 10,000 bending cycles. Following this test, the R_S 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.