Conjugated polymer-perovskite quantum dot (MDMO-PPV:CsPbBr3) nanocomposites: Miscibility, nano-structures, and properties

All-inorganic cesium lead bromide (CsPbBr₃) quantum dots (QDs) have received a surge of attention in the field of light-emitting diode (LED) display and lighting. Hence, it is interesting to study the composite film composed of CsPbBr₃ and light-emitting MDMO-PPV matrix polymer. In this study, we investigate the phase behavior among the components, MDMO-PPV, toluene (solvent), and oleic acid and oleylamine (the surface ligands for QDs) based on the Flory-Huggins theory with the group contribution method for the first time. Here we find that the MDMO-PPV and ligand molecules are immiscible whereas MDMO-PPV and toluene are partially miscible. Then through the x-ray diffraction (XRD) patterns, we demonstrate that CsPbBr₃ QDs form a nanoscale domain with ∼33–52 nm crystallites in the MDMO-PPV matrix. Furthermore, the scanning electron microscope (SEM) images display that CsPbBr₃ QDs can be highly aggregated at MDMO-PPV:CsPbBr₃= 50:50 composition. Then, through the ultraviolet-visible (UV–vis) and photoluminescence (PL) spectra, the enhancement of PL intensity is observed at ∼30–50 wt% CsPbBr₃. Finally, the electrochemical impedance spectra indicate that the composite film exhibits less resistance (∼3.2×10⁴ Ω) than the pure MDMO-PPV film (∼1.4×10⁷ Ω), suggesting that the MDMO-PPVCsPbBr₃ composite approach is promising for electrochemical and optoelectronic applications.