Enhanced optical, electrical, and mechanical characteristics of ZnO/Ag grids/ZnO flexible transparent electrodes

This study demonstrates well-designed tri-layer flexible transparent conducting electrodes (TCEs), whose structure is ZnO (20 nm)/Ag grids (4, 6, 8, 10 nm)/ZnO (20 nm) (ZAZ), fabricated via thermal deposition. The optical, electrical, and mechanical characteristics of the proposed structure are improved compared to those of MoO₃/Ag grids/MoO₃ (MAM) electrodes. The transmittance at 550 nm, sheet resistance, and figure of merit of the proposed ZAZ electrodes with 6-nm silver grids are 78.58%, 9.3 Ω/square, and 9.6 × 10^-3, respectively, which are better than those of MAM electrodes (66.25%, 9.7 Ω/square, and 1.6 × 10^-3, respectively). It is found that the enhancement of the electrical characteristics of ZAZ can be ascribed to the improved crystallization of ZnO films. ZnO films with improved crystallization and a larger grain size can inhibit carriers from scattering at inter-grain boundaries. Based on a bending test, the strains of ZAZ electrodes under tension and compression were 0.616%, 0.633%, and those of MAM electrodes were 0.62% and 0.65%, respectively. The sheet resistance of the ZAZ structure increases significantly after 800 bending cycles, while that of the MAM structure increases significantly after only 200 bending cycles. These data indicate that ZAZ electrodes have significantly improved mechanical properties and durability compared to those of MAM electrodes in the bending test under both tensile and compressive stress. The proposed TCEs show good optical, electrical, and mechanical characteristics and have potential for application in optoelectronics.