Simplified Inverted Polymer Light-Emitting Diodes using Metal Foils as Both a Cathode and Substrate

Abstract

We present inverted polymer light-emitting diodes (PLEDs) that use stainless steel (STS) as both a substrate and cathode. By employing mechanical and chemical planarization techniques and depositing a ZnO electron injection layer, we significantly reduce the surface roughness of STS substrate from 170 nm to 0.9 nm in root-mean-square value, effectively mitigating leakage current in the devices. The introduction of a Cs2CO3 electron injection interlayer on the ZnO layer successfully reduces the workfunction and the electron injection barrier between STS and the emitting layer. For the semi-transparent top anode, we utilize a MoO3 (5 nm)/Ag (15 nm)/MoO3 (45 nm) structure, which exhibits 70% transparency at a wavelength of 550 nm. The fabricated inverted PLED s on STS demonstrate a current efficiency of 3.3 cd/A and a maximum luminance of 2,450 cd/m2, and show uniform light emission under bending in air. This demonstration shows the potential of utilizing metal foils for the development of flexible and air-stable PLEDs, opening up their possibilities for future applications in flexible display technology.