High Brightness Fluorescent White Polymer Light-Emitting Diodes by Promoted Hole Injection via Reduced Barrier by Interfacial Dipole Imparted from Chlorinated Indium Tin Oxide to the Hole Injection Layer PEDOT:PSS

We demonstrated that introducing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as a hole transport layer (HTL) on top of chlorinated indium tin oxide (Cl-ITO) anode can lead to a deeper highest occupied molecular orbital level of the HTL (promoting from 5.22 to 5.42 eV) due to the interfacial dipole imparted by the Cl-ITO, which allows barrier-free hole injection to the emitting layer with polyspirobifluorene doped with the yellow emitter rubrene and significantly prevents excitons quenching by residual chlorine radicals on the surface of Cl-ITO. By use of poly[9,9-bis(6′-(18-crown-6)methoxy)hexyl)fluorene] chelating to potassium ion (PFCn6:K + ) as electron injection layer and air-stable high work function ( E Φ ) metal aluminum as the cathode, the performance of fluorescent white polymer light-emitting diode (WPLED) achieves the high maximum brightness ( B max ) of 61 523 cd/m 2 and maximum luminance efficiency (η L, max ) of 10.3 cd/A. Replacing PFCn6:K + /Al cathode by CsF/Al, the B max and η L, max are promoted to 87 615 cd/m 2 (the record value in WPLED) and 11.1 cd/A, respectively.