One-step direct patterning of flexible and transparent InGaTiO/AgPdCu/InGaTiO multi-layer electrodes for flexible organic light-emitting diodes

We developed a one-step simple wet etching process for flexible Ga, Ti co-doped In2O3 (IGTO)/AgPdCu (APC)/IGTO multi-layer electrodes deposited on colorless polyimide (CPI) substrates for flexible bottom emission organic light-emitting diodes (OLEDs). To fabricate OLEDs, the transparent and flexible IGTO/APC/IGTO multilayer electrode with a low sheet resistance of 8.35 Ohm/square and high average transmittance of 82.65 % was directly patterned using a mixed etchant of oxalic acid and nitric acid. For direct patterning of the IGTO/APC/IGTO electrode, wet etching condition was optimized as a function of etch rate, mixture solution ratio, and process temperature. At optimal wet etching condition with oxalic acid of 1 M and nitric acid of 0.79 M at 30 ℃, we successfully patterned the IGTO/APC/IGTO multi-layer without residue by one-step wet etching process. To demonstrate the feasibility of one-step patterned IGTO/APC/IGTO bottom electrode, we fabricated typical bottom emission (OLEDs) on the patterned IGTO/APC/IGTO electrodes. The performance of the flexible OLEDs with the patterned IGTO/APC/IGTO multi-layer electrodes was similar to that of rigid OLEDs with reference ITO electrodes, demonstrating the effectiveness of one-step wet etching as an effective patterning process for flexible IGTO/APC/IGTO multi-layer electrodes.