Feasible Modification of PEDOT:PSS by Poly(4-styrenesulfonic acid): a Universal Method to Double the Efficiencies for Solution-Processed Organic Light-Emitting Devices.

A feasible, universal, and low-cost strategy for solution-processed organic light-emitting devices (OLEDs) was provided to significant enhance the electroluminescent performances. The commercially available poly(4-styrenesulfonic acid) (PSSA) aqueous solution was mixed into poly(styrene sulfonic acid)-doped poly(3,4-ethylenedioxythiphene) (PEDOT:PSS) to modify its chemical and physical properties. The corresponding work-function can be easily elevated from 5.04 to 5.63 eV. The PSSA modified PEDOT:PSS is found to be a universal method to demonstrate highly efficient OLEDs with different solution-processed host/emitter combinations, covering phosphorescent and thermally activated delayed fluorescence (TADF) devices. The benchmarking solution processed OLEDs based on 2,4,5,6-tetrakis(carbazol-9-yl)-1,3-dicyanobenzene (4CzIPN) and bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) achieved the maximum EQEs of 26.6% and 22.4%, respectively, simply by modifying PEDOT:PSS with PSSA, corresponding to the improvement factors of 2.7 and 2.2. It is confirmed that such performances originate simultaneously from reduced interfacial fluorescence quenching, elevated work-function and reduced lateral conduction of the common-used PEDOT:PSS (Clevios P VP Al 4083).