Solution-Processed Fabrication of Light-Emitting Diodes\nUsing CsPbBr₃ Perovskite Nanocrystals

Abstract

The sonochemical synthesis of CsPbBr₃ perovskite nanocrystals (PNCs) is an attractive method for\nthe large-scale synthesis and low-cost production of PNC at low temperature;\nhowever, there are no reports on their application to robust film\nformation and light-emitting diodes (LEDs). In this study, ultrasonic-assisted\nsynthesis of CsPbBr₃ PNCs was reported by using precursors\n(Cs₂CO₃ and PbBr₂) and ligands (oleic\nacid (OA) and oleylamine (OAm)). The ratios of the Cs₂CO₃:PbBr₂ and OA:OAm were controlled to enhance the\nphotoluminescence (PL) of the PNCs. Furthermore, by adjusting these\nratios, we observed the transition of the PNCs from the rhombohedral\nCs₄PbBr₆ phase to the monoclinic CsPbBr₃ phase. In addition, by optimizing the Cs₂CO₃:PbBr₂ and OA:OAm ratios, we obtained CsPbBr₃ PNCs with the highest PL intensity in both solutions and\nfilms. Finally, a high-quality PNC-coated film was obtained by purifying\nthe CsPbBr₃ PNCs with methyl acetate (MeOAc) and used for\nLED device fabrication whereby the MeOAc provided solvent orthogonality\nduring the electron transport layer (ETL) coating. Thus, a solution-processed\nPNC-LED comprising dual ETLs of 2,2′,2″-(1,3,5-benzinetriyl)­tris­(1-phenyl-1<i>H</i>-benzimidazole) (TPBi) and ZnO nanoparticles was fabricated.\nThe dual ETL PNC-LED device showed enhanced LED device performance\n(lower turn-on voltage and high brightness) compared to the single\nETL PNC-LED device. Furthermore, improved charge balance was achieved\nby using a Mg-doped ZnO ETL.