Ligands for CsPbBr3 perovskite quantum dots: The stronger the better?

Surface ligands play important roles in synthesis, surface passivation, colloidal stability, and modulation of optoelectronic properties for quantum dots (QDs). It is well known that conventional ligands exhibit weak binding on the surface of perovskite QDs (PQDs), resulting in uncontrolled growth and unsatisfied stability during purification and operation. This impedes the device performance progress and practical applications severely. Stronger ligands anchoring on PQDs tightly and passivating surface defects efficiently have been reported to solve the problems. Herein, we choose a representative strong ligand, dodecylbenzene sulfonic acid (DBSA), to investigate its influence on PQD growth, stability under high-temperature with various solvents and additives, and the possibility of core–shell structure construction. Interestingly, the DBSA capped PQDs exhibit abnormally ripening under above conditions. Besides, a new mechanism for ion migration suppression is proposed based on internal lattice relaxation and inter-particle migration pathway elimination. Although DBSA-PQDs can be purified several times and maintain a high quantum yield, the corresponding light-emitting diodes show poor external quantum efficiency, which might be assigned to the unbalanced colloidal stability and film conductivity. This work indicates that strong ligands provide wider space for PQD modulation and the balance between stability and device performance should also be considered.