Low resistive transparent and flexible ZnO/Ag/ZnO/Ag/WO3 electrode for organic light-emitting diodes

Transparent electrodes cannot easily be created with high transmittance and low sheet resistance simultaneously, although some optoelectronic devices, such as large organic light-emitting diode (OLED) displays and lightings, require very low resistive transparent electrodes. Here, we propose a very low resistive transparent electrode (∼1.6 Ω/sq) with a high transmittance (∼75%) for OLED devices, the transmittance level of which represents the highest reported value to date given such a low sheet resistance level. It consists of a stacked silver (Ag)/zinc oxide (ZnO)/Ag multilayer covered by high refractive index dielectric layers. The proposed multilayer electrode with optimal layer thicknesses has a high and wide spectral transmittance peak due to interference. The low sheet resistance is a result of two Ag layers connected via the sandwiched ZnO layer. In addition to its low sheet resistance coupled with high transmittance, the proposed multilayer electrode has good flexibility. An OLED with an anode of the stacked Ag/ZnO/Ag multilayer shows performance comparable to that of an anode of indium tin oxide.

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► We propose a low resistive transparent and flexible electrode (∼1.6 Ω/sq) for OLEDs.
► The electrode consists of an Ag/ZnO/Ag multilayer covered by high index layers.
► The low resistance is due to two Ag layers connected via the sandwiched ZnO layer.
► The high optical transmittance (∼75%) is a result of the suppressed reflection.
► The ZnO/Ag/ZnO/Ag/WO3 based OLED shows performance comparable to an ITO based OLED.