Robust Transparent and Conductive Gas Diffusion Multibarrier Based on Mg- and Al-Doped ZnO as Indium Tin Oxide-Free Electrodes for Organic Electronics

Abstract

Thin-film encapsulation is strictly required to protect transparent, flexible organic light-emitting diodes (OLEDs) based on plastic substrates with poor moisture barrier performances against water vapor and oxygen. However, additional encapsulation process makes OLED fabrication complex and expensive, resulting in lower yield and higher costs for the manufacture of OLEDs. Therefore, to develop simple, transparent conductive gas diffusion barrier (TCGDB) technologies by providing barrier performances to electrodes can be alternatives. Furthermore, TCGDB based on dielectric/metal/dielectric structures exhibit not only excellent barrier performances to protect metallic and organic layers against the ambient environment but also mechanical flexibility overcoming the brittleness of oxides. In this work, to improve the moisture-resistant, electrical, and optical properties of ZnO film, periodical dopant layers were inserted during the deposition of atomic layer deposition ZnO film. These dopant layers make the intrinsic ZnO film more optically and electrically functional. The dopant of MgO with a wide band gap enables blue-shifted optical transmittance, and the dopant of Al atoms makes doped ZnO more electrically conductive. In addition, these dopant layers in the ZnO film interrupt the film crystallization, making the film less crystalline with fewer channels and grain boundaries. This effect results in significant improvement of its GDB properties. With a functional and material design that takes full advantage of the synergetic combination of highly flexible conductive Ag and a moisture-resistant MAZO layer, the MAZO/Ag/MAZO (MAM) multilayer with a thickness of approximately 110 nm achieves a sheet resistance of 5.60 Ω/sq, an average transmittance of 89.72% in the visible range, and a water vapor transmission rate on the order of 10 g/m/day. In addition, OLEDs with the MAM electrode demonstrated a great potential of indium tin oxide- and encapsulation-free organic electronics.

Textile Display with AMOLED Using a Stacked-Pixel Structure on a Polyethylene Terephthalate Fabric Substrate

“…The washing problem is a large obstacle to overcome for practical applications of electronic textiles including AMOLED textile displays. Recently, articles concerning water resistant encapsulation layers for e-textiles have been reported [25,26]. They have successfully protected the underlaid OLEDs on a fabric without performance deterioration, even after being washed 10 times.…”

Thin film encapsulation for the organic light-emitting diodes display via atomic layer deposition

“…The thickness optimization of Ag layer is crucial for the device performance, in which a discontinuous Ag layer leads to the nonuniform heat transfer, whereas a thick layer leads to the low transparency. The kick point where the Ag film turned from discontinuous to continuous was shown photographically by the AFM or SEM, and it could also be deduced by the sharp decrease in the sheet resistance [57].…”

“…photographically by the AFM or SEM, and it could also be deduced by the sharp decrease in the sheet resistance[57]. The overall structure was optimized via optical simulation via Matlab software, and it was found that the transmittance of Al 2 O 3 /Ag/Al 2 O 3 structure was 33% higher than that of the Al 2 O 3 /Ag structure due to the anti-reflection effect[123].…”

Multi-directionally wrinkle-able textile OLEDs for clothing-type displays

“…The gas barrier and the OLED were deposited on the textile platform, and the liquid passivation on which the gas barrier had formed was laminated to the OLED. The gas barrier that functioned as the OLED encapsulation to block moisture and oxygen 31 was fabricated using a spacer polymer 32,33 and the nano-stratified barrier of Al 2 O 3 and ZnO quasi-films [34][35][36][37][38] . The porous and defect-decoupling characteristics of the nanostratified structure enhanced the structural flexibility and barrier property.…”