Self-Assembled Molecule Doping Enables High-Efficiency Hole-Transport-Layer-Free Perovskite Light-Emitting Diodes

摘要

Hole-transport-layer-free (HTL-free) perovskite light-emitting diodes (PeLEDs)are attracting increasing research attention because of their simplified devicestructure, fast preparation process, and high cost effectiveness. However,their much lower external quantum efficiency (EQE) as compared with theconventional p-i-n type ones has considerably limited their applicationprospects. Here, a self-assembled molecule (SAM) doping strategy isproposed by introducing 4-(3,6-dimethyl-9H-carbazol-9-yl) butyl phosphonicacid (Me-4PACz) containing P=O functional groups into the perovskiteprecursor solution and preparing the HTL-free quasi-2D perovskite filmsthrough the one-step spin-coating process. The doped Me-4PACz moleculescan not only accumulate at the ITO/perovskite interface to lower the holeinjection barrier, but also extend deep into the perovskite layer to suppress thetrap density in perovskite films and regulate the crystallization process formonodispersed phase composition. With the further addition of ethoxylatedtrimethylolpropane triacrylate small molecule containing C=O groups topassivate the defects synergistically with Me-4PACz, the EQE of thecorresponding device is boosted from 1.5 to 16.7 together with a 3.5-foldincrease in operational stability, which is the highest efficiency reported so farfor HTL-free PeLEDs. The results demonstrate that the SAM doping strategycan be a viable and facile way to prepare high-performance HTL-free PeLEDsfor practical applications.