Enhanced device performance via interface engineering in polymer-based optoelectronic devices

Achieving efficient electron transport is challenging owing to the large energy barrier between the conduction band of n-type metal oxide and the lowest unoccupied molecular orbital (LUMO) of the emissive layer in inverted polymer light-emitting diodes (PLEDs) or the active layer in inverted polymer solar cells (PSCs), which results in unbalanced charge transport, leading to low device efficiencies. Herein, we have demonstrated that the device performance could be enhanced in both PLEDs and PSCs by treating either the interface between the electron transport layer (ETL) and the emissive layer in PLEDs or the active layers with self-assembled dipole monolayer (SADM), ionic liquid molecules (ILM) and polar solvent (PS). The interface engineering results in a reduction of the energy barrier, which results in enhanced electron transport in both devices. Especially, optimized PLEDs and PSCs show an external quantum efficiency (EQE) of 1.38% and a power conversion efficiency (PCE) of 4.21%, which are enhanced by approximately 138- and 1.37-fold, respectively, compared to the reference devices.