Research Toward The High Flexible Electrode Applied To Organic Electronics

OLED is considered to be a new generation display technology after the liquid crystal display(LCD) on account of many advantageous features, such as active light emitting, ultrathin, fast response speed, can be made into large area devices, ect. It is known as “dream displays” by which can realize flexible foldable displays. However, flexible OLED is limited by many reasons. Among them, flexible substrate and electrode are two crucial factors. In this paper, we combine Ag nanowire(Ag NW) with photopolymer film. Flexible OLED is obtained which Ag NW used as flexible transparent electrode and photopolymer as flexible substrate. We through mechanical bending test verify that Ag NW-photopolymer film has a good bending performance. The performance of Ag NW electrode is further improved after combined zinc oxide(Zn O) prepared by low-temperature(60°C) atomic layer deposition(ALD) with Ag NW meshes.First of all, the flexible electronic technology was reviewed. Then the development of flexible OLED was summarized. Furthermore, some critical factors of flexible OLED were analyzed including mechanical properties、lifetime、optical properties and electrical properties. We used these as a research foundation for this topic.The Ag NW electrode on photopolymer substrate was created using a substrate peel-off process combined with a spin-coating process. The root mean square(RMS) roughness of this kind of electrode was similar with Si substrate, which guaranteed a good performance of the flexible OLED. We optimized the concentration of Ag NW solution and choose 5mg/ml to prepare the Ag NW electrode. The sheet resistance was 45.7Ω/口.The highest current efficiency of flexible OLED is 13cd/A, which could be comparable with traditional ITO-PET OLED at the same device structure. The Ag NW-photopolymer film could keep stable mechanical flexibility at bending a radius of 2mm.To improve the performance of Ag NW electrode further, we proposed a hybrid flexible electrode which combined Ag NW meshes with Zn O grown by low temperature ALD process. Zn O could sufficient fill voids between Ag NWs, making contact more efficiently. Moreover, Zn O improved interfacial contact between Ag NW and organic layers. As a result, the performance of carriers injection/extraction has been improved. Furthermore, we fabricated hole-only devices to certify the function of Zn O grown at low temperature. To conclude, the Zn O film grown at low temperature brought significant contribution to improve the performance of the modified Ag NW electrode.