Perovskite nanocrystals (PCNs) exhibited excellent absorption and luminescent optical properties.Inorganic silica nanohelices are used as chiral templates to induce optically active properties to CsPbBr3 PNCs grafted on their surfaces. In suspension, PNCs synthesized and grafted on the right (or left) handed silica helices do not show any detectable chiroptical properties. In contrast, in a dried film state, they show large circular dichroism (CD) and circularly polarized luminescence (CPL) signals with dissymmetric factor up to 6*10 -3 . Grazing incidence X-ray scattering, tomography electron microscopy (EM) and cryo EM have shown closely and helically packed PNCs if the nanohelices@PNCs are dried in contrast to much more loosely organized PNCs solvated in suspension. Simulations based on the coupled dipole method (CDM) demonstrate that the CD comes from the dipolar interaction between PNC assembled into a chiral structure. We show that the CD decreases as the interparticle distance increases. These results indicate that closely packed and helically arranged PNCs on silica nanohelices result in an increase of the optically active properties in the film state.

The polarization property of CsPbX3 perovskites have been observed and studied systematically in this paper.

Trap states in colloidal quantum dot (QD) solids significantly affect the performance of QD solar cells, because they limit the open-circuit voltage and short circuit current. The {100} facets of PbS QDs are important origins of trap states due to their weak or missing passivation. However, previous investigations focused on synthesis, ligand exchange, or passivation approaches and ignored the control of {100} facets for a given dot size. Herein, trap states are suppressed from the source via facet control of PbS QDs. The {100} facets of ≈3 nm PbS QDs are minimized by tuning the balance between the growth kinetics and thermodynamics in the synthesis. The PbS QDs synthesized at a relatively low temperature with a high oversaturation follow a kinetics-dominated growth, producing nearly octahedral nanoparticles terminated mostly by {111} facets. In contrast, the PbS QDs synthesized at a relatively high temperature follow a thermodynamics-dominated growth. Thus, a spherical shape is preferred, producing truncated octahedral nanoparticles with more {100} facets. Compared to PbS QDs from thermodynamics-dominated growth, the PbS QDs with less {100} facets show fewer trap states in the QD solids, leading to a better photovoltaic device performance with a power conversion efficiency of 11.5%.

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