maximum (FWHM) and current efficiency (CE) of the TEOLEDs are significantly optimized owing to the micro-cavity effect of the top-emitting structure, promoting the applications in ultra-high-definition displays and micro-displays. [11,12] However, one major challenge of the TEOLEDs is the severe waveguide and plasmonic losses, which hinders the light outputcoupling and results in the low external quantum efficiency (EQE). [13,14] Introducing the localized surface plasmon resonance (LSPR) in the device is an effective way to increase the EQE of the OLEDs. [15,16] The LSPR is generated by overlapping the local electromagnetic field of excitons in the emitting layer and the surface plasmons of the noble metal in form of the nanowire and nanoparticles (NPs). [17][18][19][20][21] When the absorption peak of the metal NPs matches the emission wavelength of the device, the local electromagnetic fields around the NPs at a specific wavelength are enhanced. [22,23] More importantly, the LSPR is greatly influenced by the size of the noble metal NPs. [24,25] By precisely adjusting the size and the spacing of the NPs, the resonance wavelength of the NPs can be tuned to well match the wavelength of the electroluminescence (EL) spectra of OLEDs. [26,27] However, there are few reports on the effect of the LSPR on the inverted TEOLEDs.In this study, we have introduced a light output-coupling layer (LOCL) composed of AgNPs and MoO x on the top capping layer (CPL) of the inverted TEOLED device. The AgNPs in the LOCL could significantly improve the light output-coupling of the TEOLED owing to the LSPR, and the MoO x in the LOCL could effectively protect the water-and oxygen-sensitive electron injection material. In addition, the FWHM is narrowed to 50 nm due to the micro-cavity effect of the top-emitting structure and the turn-on voltage (V on , calculated at the lowest brightness of ≈1 cd m −2 ) is decreased to 2.6 V with Ag 2 O doped 4,7-diphenyl-1,10-phenanthroline (Bphen) as electron injection layer (EIL). Through systematical analysis and the finite difference time domain simulation (FDTD), we found that when the thickness of the AgNPs was 0.5 nm and the thickness of MoO x was 20 nm, the light output-coupling of the device reached the best. The CE and the EQE were increased 1.53 and 1.3 times to 28.3 cd A −1 and 13.11%, and the luminance achieves 34 247 cd m −2 .In this study, a light out-coupling layer (LOCL) composed of Ag nanoparticles (NPs) and MoO x is introduced on top of the inverted top-emitting organic light-emitting diode (OLED). The full width at half maximum (FWHM) is narrowed to 50 nm due to the micro-cavity effect of the top-emitting structure and the turn-on voltage is as low as 2.6 V. The AgNPs in the LOCL significantly improves the light output-coupling of the OLED owing to the localized surface plasmon resonance, and the MoO x in the LOCL effectively protects the water-and oxygen-sensitive electron injection material. As a result, the performance of the OLED with the LOCL is significantly enhanced. The maximum...

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