Kinetics and mechanism of light-induced phase separation in a mixed-halide perovskite

Perspective on High-Resolution Characterizations of Polarons in Halide Perovskites

“…Another example is TEM specimen holders with integrated fiber optics for in situ light excitations and collections. Phase separation in CsPbI x Br 3– x perovskite single crystals driven by light was investigated using this technique . The phase separation process and its dynamics are visualized on the nanometer scale at cryogenic temperatures using in situ STEM and cathodoluminescence.…”

Stable and Efficient Mixed‐halide Perovskite LEDs

“…[51b] N-gradients stem from the exponential reduction of I exc within films, resulting in either photoinduced lattice strain or depth-dependent thermalization of carriers across the material. [49] Both acts to promote anion migration. For the latter electric field schemes, two ideas have been proposed.…”

“…[48] A final group of models propose that the demixing of halides is caused by the interaction of photogenerated carrier gradients or electric fields with point defects, coupled with variations in halide mobilities. [49]…”

“…It's worth noting that in the polaron model, the appearance of the excitation intensity threshold occurs when the lattice , c) Reproduced with permission. [49] Copyright 2023, Springer Nature. distortion caused by polarons overcomes cohesive energy, leading to segregation (Figure 5c, d).…”

Synchronously Polishing the Lead-Rich Surface and Passivating Surface Defects of CsPb(Br/I)3 Quantum Dots for High-Performance Pure-Red PeLEDs

“…Mixed-halide perovskite quantum dots (QDs) afford a very facile way to adjust emission through changing the ratio of different halides, making CsPb­(Br/I) 3 QDs exhibit a bright applying prospect in pure-red PeLEDs. − However, for the dynamic bonding between native ligands (oleylamine (OAm) and oleic acid (OA)) and the QDs, these ligands can be easily stripped off during the isolation/purification process, resulting in undercoordinated Pb 2+ clusters at the surface of the QDs. , These undercoordinated Pb 2+ clusters consist of imperfect Pb­(Br/I) 6 4– octahedra with halide vacancies, which are regarded as the lead-rich surface for the perovskites . The traps relevant to lead-rich surface were n states, and these n traps with deep-energy-level natures would pin the Fermi energy levels ( E f ) around the conduction band edge (CB), resulting in poor hole transportation and serious nonradiative recombination. , Furthermore, due to the ionic nature of perovskite materials and the weak van der Waals forces between Cs + and X – of the [PbX 6 ] 4– octahedron, halide ion migration is usually observed in CsPb­(Br/I) 3 QDs under an electric field, which results in shifted EL and device degradation. − Moreover, the halide vacancies on the lead-rich surface of the QDs usually serve as channels for halide ion migration, which accelerates halide ions in rearranging and forming Br-rich and I-rich regions, leading to severe phase separation in the CsPb­(Br/I) 3 QDs. − As discussed above, the lead-rich surface is considered to be the key factor affecting the performance of pure-red PeLEDs based on CsPb­(Br/I) 3 QDs. To date, the most commonly used method to eliminate the surface defects of QDs is to find a new ligand with a stronger bonding with lead ions. , Although this is very effective for improving the efficiency and stability of the materials and devices, it cannot remove the lead-rich surface of QDs thoroughly.…”