Improved stability of CsPbBr3 perovskite quantum dots achieved by suppressing interligand proton transfer and applying a polystyrene coating

All-inorganic lead halide perovskite quantum dots (PQDs) have shown great promise for optoelectronic applications due to their unique optical and electrical properties. However, their poor stability against moisture, UV light or thermal attacks greatly hinders their practical applications. One of the reasons for this instability is the proton transfer between oleic acid (OA) and oleylamine (OLA), which induces serious ligand loss. The idea of this work is to prevent the interligand proton transfer by replacing OLA with cetyl trimethylammonium bromide (CTAB) that cannot be protonated. The synthesized CsPbBr3 PQDs in solution show high photoluminescence quantum yields up to 71% and also exhibit higher stability against acetone than the counterparts synthesized using oleylammonium bromide (OLABr). Subsequently, CsPbBr3 PQDs with a peak wavelength of 515 nm (g-CsPbBr3) synthesized using CTAB are further composited with a polymer of carboxyl-functionalized polystyrene (cPS). The composite shows enhanced thermal and moisture stability. It is demonstrated that this green-emitting composite can produce high color gamut (130%) white light-emitting diodes when combined with the K2SiF6:Mn4+ phosphor and a blue InGaN chip, enabling its use in display backlights.