| 초록 |
A transparent conductive layer is an essential component in thin film optoelectronic devices such as light emitting diodes and photovoltaic cells to provide electrical contact and optical in- and out-coupling. Indium tin oxide (ITO) is a representative material for the transparent electrode, because of its astonishing figure of merit, i.e., electrical to optical conductivity ratio. However, unfortunately, it is well known that the ITO is completely unsuitable for flexible devices owing to its brittle nature. Several candidate materials are considered for replacement of the ITO in the optoelectronic devices, but we paid attention to a strong possibility of Ag nanowires mainly supported by their metallic nature (outstanding electrical conductivity and flexibility) and high aspect ratio. Recently, it is widely accepted that the Ag nanowires could be positioned to be an excellent alternative to the ITO, however, they also have a number of potential issues, e.g., the performance of thin film devices based on the Ag nanowire electrodes may deteriorate because of their surface roughness, and the adhesion of the nanowires to the substrate may not be proper. Here we propose a new method to embed the Ag nanowires into the transparent polymer substrate, so that could make a flexible and smooth electrode. There was no increase of electrical resistance even after the fabricated sample was bent with a bending radius of less than 100 um. Under a bending cyclic test of 105 cycles with a bending radius of 500 um, the change of the resistance was also negligible. The root mean square value of the surface roughness was measured to be less than 1 nm, which means that it is perfectly suitable for the substrate of thin film devices. We fabricated an organic light emitting diodes using the substrates, and it was proved that ultra-flexible and highly competitive light emitting diodes could be made by employing the proposed way. |
