Boosting the efficiency of quasi-2D perovskite light-emitting diodes via tailoring the PEDOT:PSS hole transport layer

In quasi-2D perovskite light-emitting diodes (PeLEDs), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS) has been widely used as the hole transport layer because of its high conductivity, high optical transparency, flexibility, and good water processability. However, pristine PEDOT:PSS has large energy level offset, severe interfacial excitons quenching, and is unfit for high quality quasi-2D perovskite growth, making PeLEDs less efficient. In this work, we developed a facile method to tune PEDOT:PSS layer with different PSSNa concentrations by introducing excessive PSSNa into PEDOT:PSS film and significantly improve the external quantum efficiency (EQE) of PeLEDs. The modified PEDOT:PSS film is significantly smoother than the pristine film and resulting a better perovskite morphology. The richness of surface PSS also reduces nonradiative exciton quenching and lowers the hole injection barrier from 0.7 eV to 0.4 eV. Owing to these improvements, the EQE of our devices increased from 4.9% to 11.3%.