All-Solution-Processed Multilayered White Polymer Light-Emitting Diodes (WPLEDs) Based on Cross-Linked [Ir(4-vb-PBI)₂(acac)]

All-solution-processed multilayered white polymer light-emitting diodes (WPLEDs) are promising candidates for low-cost and large-area flexible full-color flat-panel displays and solid-state lighting. However, it is still challenging to improve their performance. In this work, based on an elegant strategy of orthogonal materials, the utilization of the cross-linked Ir3+ polymer film poly(NVK-co-[Ir(4-vb-PBI)2(acac)]-co-NVK) (NVK = N-vinyl-carbazole; 4-vb-HPBI = 1-(4-vinylbenzyl)-2-phenyl-1H-benzo[d]imidazole; and Hacac = acetylacetone) as the emitting layer (EML) between a hydrophilic polymer film poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the hole injection layer (HIL) and a hydrophobic polymer film poly(vinyl-PBD) (vinyl-PBD = 2-(4-(tert-butyl)phenyl)-5-(4′-vinyl-[1,1′-biphenyl]-4-yl)-2,5-dihydro-1,3,4-oxadiazole) as the electron transport layer (ETL) led to the successful fabrication of reliable all-solution-processed multilayered WPLEDs. The device exhibits a ηCEMax of 18.19 cd/A, a ηPEMax of 8.16 lm/W, and a ηEQEMax of 9.32% with stable white light (Commission International De L’Eclairage (CIE) coordinates x = 0.269–0.283, y = 0.317–0.330; corrected color temperatures (CCTs) of 7237–8199 K, and CRIs (color rendering indices) of 63–72) under a wide applied-voltage range. Its high performance, especially with record efficiencies among those of reported all-solution-processed WPLEDs, renders cross-linked Ir3+ polymers a new platform to all-solution-processed multilayered WPLEDs.