Pyridine group incorporated mixed electron transporting layers for high-performance perovskite light-emitting diodes

Abstract

The unsaturated Pb2+ ions, located at the perovskite/charge transport layer (CTL) interfaces, are one of the main trap centers that result in non-radiative recombination of perovskite light-emitting diodes (PeLEDs), thus compromising device efficiency. Therefore, interface engineering and modulation are of significance in passivating the surface defects of the perovskite film as well as modifying the perovskite/CTL interface properties. In this work, a high-mobility pyridine-based electron transport material, 1,3,5-tri(m-pyrid-3-yl-phenyl) benzene (TmPyPB), is co-evaporated with 2,2',2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) to form efficient electron-transport layers (ETLs) for PeLEDs. The interaction of the pyridine group of TmPyPB with the uncoordinated Pb2+ ions can effectively passivate the perovskite defects. Furthermore, the mixed ETL can also enhance electron mobility by tuning the mixing ratios between the TmPyPB and TPBi, thus boosting the device efficiency. As a result, PeLEDs with enhanced electron mobility and reduced defects are prepared, in which the device exhibits a maximum current density (CE) of 74 cd/A and an external quantum efficiency (EQE) of 25.4%. This EQE is nearly two fold higher than that of the pure TPBi-based PeLEDs.