Mrs. Rachel Lifer - Ph.D. Candidate
22/10/2026
David Wang Auditorium, 3rd Floor, Dalia Maydan Bldg.
13:30
Lead halide perovskite nanocrystals exhibit highly tunable optical properties, making their integration into nanoscale heterostructures particularly attractive. However, their dynamic surfaces and structural instability complicate both surface control and heterostructure growth.
My seminar focuses on two complementary approaches addressing these challenges. First, we investigate thiocyanate-based surface treatment of CsPbBr₃ nanocrystals and its passivation mechanism. Thiocyanate treatments have been shown to improve perovskite solar-cell efficiency and stability. At low loading, thiocyanate similarly acts as an effective surface passivant in colloidal perovskite nanocrystals. This reduces surface traps, significantly enhances the photoluminescence quantum yield and improves stability. Atomic-resolution HAADF-STEM analysis reveals ~3% lattice dilation at the nanocrystal surface. Together with EELS sulfur mapping, this provides evidence for thiocyanate binding at the surface, supporting a surface-binding passivation mechanism over other proposed explanations.
While low sulfur loading achieves surface passivation, further sulfur precursor addition is insufficient to drive heterostructure growth. Heterostructure formation therefore requires an additional level of synthetic control. We tune the reactivity governing colloidal growth using small perovskite clusters as reactive building blocks for heterostructure formation, yielding stable CsPbCl₃/Pb₄S₃Cl₂ heterostructures. We use thermal ramping to control nucleation and growth, forming anisotropic perovskite nanoplates for the first time. The nanoplates exhibit distinct optical properties attributed to their geometry. This strategy is extended to CsPbCl₃/PbS heteroplates, demonstrating versatility beyond a single material system.
The vision is that tuning reactivity through perovskite clusters and controlled growth strategies will enable a broader range of perovskite heterostructures for nanoscale materials engineering.