Opto-Electrically Engineered Low Haze IZO/Ag/IZO Nanomesh Electrode for Highly Flexible Blue OLED

Abstract

Although metal nanomesh (NM) has been demonstrated as a potential replacement to conventional indium tin oxide (ITO) as the flexible transparent conductive electrodes (FTCEs), it suffers from the diffraction and scattering of transmitted light that creates the optical haze [1, 2]. The persuasive methods for supressing the optical haze of NM (i.e., reducing the thickness, increasing the mesh hole size, or reducing the metal covered area), reported so far, are closely related to the conductivity of the electrode [3]. Herein, we propose a smart anti-reflective (AR) indium zinc oxide (IZO)/Ag/IZO nanomesh (IAINM) FTCEs to suppress the optical haze without affecting the conductivity of the electrode. Based on finite-domain time-difference (FDTD) simulation results, we have optimized the thickness of each top and bottom IZO layer as well as the size of holes in IAINM FTCEs. As a result, IAINM FTCEs (IZO (30 nm)/Ag(20 nm)/IZO(30 nm)) exhibited high transmittance (> 90% at 475 nm) and low sheet resistance of 9.4 Ω/sq on PET substrates. Accordingly, the optical haze of IAINM FTCEs was about 8% at 475 nm, which is 250% lower than AgNM FTCEs. Besides, the sheet resistance barely changed after 1000 bending cycles at a bending radius of 0.3 cm. Further, the blue TADF FOLEDs fabricated with the IAINM as anode exhibited improved external quantum efficiency (by 67%), current and power efficiency (by 71% and 85%, respectively) than the ITO-based OLEDs. After strain, the IAINM-based OLEDs exhibited the performance change of less than 20% while AgNM and ITO-based OLEDs showed the change of more than 30%. More detailed experimental and computational results will be presented at the conference.