The Fabrication And Investigation Of Flexible Transparent Conductive Electrode On Polyimide Substrate

Transparent conducting electrode(TCE)play a very important role in optoelectronics device such as display,lighting and solar cell panel.The tin doped indium oxide(ITO)is the universal used TCE for its high light transmittance and low resistance.However,the element indium is shortage in the world and ITO electrode is mechanically brittle,making it difficult to meet future large and diverse TCE application demand.Therefore,the new TCE materials have been widely research and the flexible transparent conducting electrode is the current hotspot.Among the materials at room temperature,the metals possess the highest conductivity due to their high free-electron.As we know,the bulk metal own highly reflective in the visible range and cannot function as a transparent electrode,although the ultrathin metals is transparent,but it get a high sheet resistance(Rsq)in consideration of the electron scattering existing in the surface and grain boundaries.Aimed at this problem,the paper mainly studied from two aspects:(1)Seed layer was used to reduce roughness of the metal surface.2 nm gold as seed layer was deposition followed by 4 nm silver,an ultrathin metal layer with roughness less than 0.5 nm and Rsq 40 ?/sq was obtained.Then varied thickness ZnO layer was deposited upon the surface of the ultrathin metal,and a transparent electrode with transmittance 82.2% in 550 nm and Rsq 35.4 ?/sq was acquired.At last,the same process was transferred to the colorless polyimide(cPI)substrate,subsequently,a flexible transparent conducting electrode with transmittance 80.8% in 550 nm and Rsq 35.2 ?/sq was achieved.In addition,the flexible TCE taking a good adhere to the cPI substrate and meanwhile has a good mechanical flexible.Inverted PLED with F8 BT as emitting layer fabricated using this electrode show maximum Luminance of 615 cd/m2 and current efficiency over 1 cd/A-1?(2)To reduce the sheet resistance for applying the TCE to large area optoelectronics device,the metal grid was utilized by photolithography straightly in cPI substrate.Commonly,it is difficult to produce a complete metal grid in cPI substrate by straight photolithographytripping method.Thus,the inorganic layers made of SiNx and SiOx are deposited on the surface of cPI using plasma enhanced chemical vapor deposition method in this paper,then photolithography,deposition and lift off,successively.Among different sizes of metal mesh,a flexible transparent conducting electrode by metal grid with transmittance 86.79% in 550 nm and Rsq 15.3 ?/sq was easy achieved.