Defect-Triggered Phase Transition in Cesium Lead Halide Perovskite Nanocrystals

Abstract

All-inorganic perovskite nanocrystals (NCs) have emerged as a class of low-cost and high-efficiency light-emitting materials. However, the structure and phase transition behavior of these NCs remain poorly understood. Here, we provide unambiguous evidence that all these properties are associated with structural defects in NCs. Using CsPbCl 3 NCs as a model system, we find that the cubic subdomains in highly defective NCs gradually convert to the orthorhombic upon cooling room-temperature quasi-cubic NCs, whereas high-quality cousins, with mixed cubic and orthorhombic subdomains at room temperature, exhibit a significant resistance for such a phase transition. Car-Parrinello molecular dynamics simulations unveil the important role of point defects in triggering a stepwise, reversible phase transition of CsPbCl 3 NCs. Importantly, we show that the defect-triggered phase transition also exists in other all-inorganic perovskite NCs. Our findings provide new insight into the structure and phase transition of CsPbX 3 NCs and highlight the important role of defects in impacting these properties.

Optical studies of semiconductor perovskite nanocrystals for classical optoelectronic applications and quantum information technologies: a review

“…When the temperature was further increased to be above 300 K, Li et al 80 found out that the inorganic perovskite NCs could be thermally deteriorated to cause an irreversible quench in the PL intensities. The temperaturedependent optical properties are also strongly dependent on the existence of defect sites, which have been shown by Ma et al 81 to cause a phase transition from cubic to orthorhombic crystal structures upon cooling all-inorganic perovskite NCs from room temperature.…”

“…With the increasing temperatures, most of the studied perovskite NCs demonstrated a blueshift in the PL peaks with broadened linewidths, as a joint effect of lattice expansion and exciton-phonon coupling. [78][79][80][81] In a very rare occasion, Wei et al 79 reported an anomalous redshift observed at 220 K in the PL peaks of CsPbBr 3 NC ensembles, which was attributed to the electronphonon coupling effect. When the temperature was further increased to be above 300 K, Li et al 80 found out that the inorganic perovskite NCs could be thermally deteriorated to cause an irreversible quench in the PL intensities.…”

Chemically Stable Black Phase CsPbI3 Inorganic Perovskites for High‐Efficiency Photovoltaics

“…Reproduced with permission. [ 115 ] Copyright 2019, American Chemical Society. d) The defect formation energies of CsPbI 3 as a function of Fermi level between the valence band maximum and conduction band minimum of native point defects calculated under lead‐rich (left) and lead‐poor (right) growth conditions.…”

“…used the case of CsPbCl 3 NCs and revealed that the structural defects dictated the structure and phase transition behaviors of all‐inorganic perovskite NCs. [ 115 ] They found that upon cooling the room temperature quasi‐cubic NCs, the cubic subdomains in the highly defective CsPbCl 3 NCs gradually converted to orthorhombic phase, while the high‐quality NCs, with mixed cubic and orthorhombic subdomains at room temperature, exhibited a significant resistance for such a phase transition (Figure 8c). Importantly, this defect‐triggered phase transition also exists in other all‐inorganic halide perovskite NCs including CsPbI 3 and CsPbBr 3 .…”

High Phase Stability in CsPbI3 Enabled by Pb–I Octahedra Anchors for Efficient Inorganic Perovskite Photovoltaics

“…In fact, such significantly reduced defect density in the CsPbI 3 is not only favored for high‐performance perovskite photoelectronic devices, but also beneficial to enhancing the photoactive phase stability via increasing the phase transition energy barrier from black phase to non‐photoactive yellow phase. [ 39,43 ]…”