A transparent composite electrode composed of AgCr and Mo-doped GaZnO to realize flexible bottom-emitting OLEDs

Abstract

We propose a new flexible transparent composite electrode that uses an ultra-thin silver-chromium (AgCr) alloy film to increase the conductivity of a Mo-doped GaZnO (MGZO) thin film and to maintain high transmittance. This optimized AgCr (7 nm)/MGZO (40 nm) composite electrode on a PET substrate achieves a high transmittance of 83.4% and an adequate sheet resistance of 11.6 Ohm sq⁻¹. The sheet resistance of this composite electrode reaches only 12.0 Ohm sq⁻¹ as the number of bending cycles increases from 0 to 10 000, demonstrating their durability against repeated bending. In addition to the absence of obvious surface cracking, the increase of root-mean-square roughness remains at the sub-nanometer level, which will not affect subsequent device processes. Benefiting from the excellent optoelectronic properties of the flexible AgCr/MGZO electrode, the bottom-emitting organic light-emitting diodes (OLEDs) with an Ir(ppy)₃ emitter gave satisfactory initial peak efficiencies of 18.9% (67.1 cd A⁻¹) and maintained peak efficiencies of 18.5% (64.3 cd A⁻¹) after bending for 10 000 cycles. These results demonstrate that the AgCr/MGZO composite films possess excellent potential for use as a transparent electrode in flexible optoelectronics applications.