Two-Dimensional Ca₂Nb₃O₁₀ Perovskite Nanosheets for Electron Injection Layers in Organic Light-Emitting Devices

We report in this article the application of calcium niobate (CNO) perovskite nanosheets for electron injection layers (EILs) in organic light-emitting devices (OLEDs). Four kinds of tetraalkylammonium hydroxides having different alkyl lengths were utilized as the exfoliation agents of a layered compound precursor HCa₂Nb₃O₁₀ to synthesize CNO nanosheets, including tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide (TPAOH), and tetrabutylammonium hydroxide. CNO nanosheet EILs were applied in fluorescent poly[(9,9-di- n-octylfluorenyl-2,7-diyl)- alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) organic light-emitting polymer-based devices. The effects of dispersion concentrations and alkyl chain length on the devices' performances were investigated. The results demonstrated that OLEDs' performances were related to the coverage ratio of the CNO nanosheets, their thicknesses, and their work function values. Among the four exfoliation agents, the device with CNO nanosheets exfoliated by TPAOH showed the lowest driving voltage. The OLEDs with the CNO nanosheet EILs showed lower driving voltages compared with the devices with conventional EIL material lithium 8-quinolate.