Highly bright and stable all-inorganic perovskite light-emitting diodes with methoxypolyethylene glycols modified CsPbBr3 emission layer

Abstract

Modifying the inorganic perovskite emission layer (EML) with polymer materials is one of the key strategies to improve the performance of perovskite light-emitting diodes (PeLEDs). However, the reported polymers, such as polyethylene glycol (PEG), typically have poor solubility in solvents [like dimethylsulfoxide (DMSO)] of perovskite precursors, which requires a pre-heating process to dissolve them. Here, methoxypolyethylene glycol (mPEG), which possesses high solubility in DMSO, is introduced into the perovskite precursors without pre-heating. The highest luminance of 33 500 cd m−2 and the maximum current efficiency of 3.14 cd A−1 are achieved in the prepared PeLED by optimizing the mPEG content in the CsPbBr3 EML, which are even better than those of the PeLEDs modified with PEG. Moreover, the optimized PeLED shows a sub-bandgap turn-on voltage of 2.3 V, which is among the lowest values of single polymer-assisted all-inorganic PeLEDs. The device stability of PeLEDs is also improved by mPEG doping in the CsPbBr3 EML, which shows no obvious decay after operating at an initial luminance of 100 cd m−2 for more than 150 min and 24 h for bare and encapsulated devices, respectively. Our work reveals the great potential of the polymer, mPEG, in modifying the CsPbBr3 EML film for highly bright and stable PeLEDs.