| Title |
Optimization of Flexible, Transparent TiO2/Cu/ZnO Electrodes by Simultaneous Suppression of Optoelectrical Losses and Pinhole Formation |
| Authors |
정은욱(Eunwook Jeong); 이건환(Gun-hwan Lee); 조영래(Young-rae Cho); 윤정흠(Jungheum Yun) |
| DOI |
https://doi.org/10.3365/KJMM.2019.57.5.316 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
transparent electrodes; flexible substrates; oxide/metal/oxide; copper; pinholes; current leakage |
| Abstract |
We demonstrated an effective method for fabricating a highly efficient flexible transparent electrode in an oxide/metal/oxide configuration based on an ultrathin Cu film. It exhibited low losses in optical transmittance and electrical conductivity while minimizing current loss due to pinhole-related leakages. The Cu film was developed on a chemically heterogeneous ZnO film into a completely continuous and pinhole-free layer with a reduced thickness of approximately 6 nm. This was accomplished using a simple, but highly effective, room-temperature reactive sputtering technique with precisely controlled oxidation of Cu. The pinhole-free morphology of the ultrathin Cu(O) film is attributed to the dramatically improved wetting ability of Cu(O) in the presence of a trace amount of oxygen (ca. 2-3 at%). The synthesis of a completely continuous, ultrathin Cu(O) film in an oxide/metal/oxide configuration, consisting of the Cu(O) film is sandwiched between top TiO2 and bottom ZnO films on a polymer substrate, for making a flexible transparent electrode with excellent transparency and no notable current leakage. The superior optoelectrical performance of the TiO2/ Cu(O)/ZnO electrode clearly exceeded that of the same geometric configuration using a pure Cu film of the same thickness. The optimized electrode exhibited an average transmittance of 80.8% in the spectral range of 400- 800 nm and a sheet resistance of 13 Ω sq-1. The proposed TiO2/Cu(O)/ZnO electrode was proven as a promising alternative to ITO, and demonstrated excellent mechanical flexibility on flexible polymer substrates.(Received March 18, 2019; Accepted March 28, 2019) |