Time-resolved photoluminescence study of excitonic relaxation in one-dimensional systems

Broadband white light emission from one-dimensional zigzag edge-sharing perovskite

We reported 1D (AMP)PbBr₄ and (AMP)PbCl₄ perovskites, which consisted of the 1D zigzag edge-sharing [PbBr₄²⁻ (or PbCl₄²⁻)]_∞ infinite inorganic chains with AMP²⁺ cations, for the white-light emission.

One-dimensional organic lead halide perovskites with efficient bluish white-light emission

Organic-inorganic hybrid metal halide perovskites, an emerging class of solution processable photoactive materials, welcome a new member with a one-dimensional structure. Herein we report the synthesis, crystal structure and photophysical properties of one-dimensional organic lead bromide perovskites, C₄N₂H₁₄PbBr₄, in which the edge sharing octahedral lead bromide chains [PbBr₄ ^2-]_∞ are surrounded by the organic cations C₄N₂H₁₄ ²⁺ to form the bulk assembly of core-shell quantum wires. This unique one-dimensional structure enables strong quantum confinement with the formation of self-trapped excited states that give efficient bluish white-light emissions with photoluminescence quantum efficiencies of approximately 20% for the bulk single crystals and 12% for the microscale crystals. This work verifies once again that one-dimensional systems are favourable for exciton self-trapping to produce highly efficient below-gap broadband luminescence, and opens up a new route towards superior light emitters based on bulk quantum materials.

Femtosecond dynamics of exciton localization: self-trapping from the small to the large polaron limit

We use femtosecond vibrational wavepacket techniques to time-resolve the coupled electronic and vibrational dynamics of exciton self-trapping in a series of materials in which the relative strength of the electron-phonon coupling can be compositionally tuned from the small to the large polaron limit. Transient absorption experiments are carried out in the quasi-one-dimensional halide-bridged mixed-valence transition metal linear chain complexes [Pt(en)2][Pt(en)2X2]⋅(ClO4)4 (en=ethylenediamine, C2H8N2) with X=Cl, Br and I. In each complex, we detect the formation of the self-trapped exciton through the appearance of its characteristic red-shifted optical absorption, and find that self-trapping occurs on a time scale of the order of a single vibrational period of the optical phonon mode that dominates the self-trapping dynamics. The associated optical phonon response, detected as wavepacket oscillations that modulate the exciton absorption, shows a significant softening of the optical phonon frequency compared to that of the unexcited system. The degree of softening is found to vary significantly with coupling strength, ranging from more than 40% in the strongly coupled chloride-bridged complex to less than 20% in the weakly coupled iodide-bridged complex. We relate these results to the extent of electronic delocalization by comparison with the electronic properties of the ground states of the materials and with the properties of their equilibrated self-trapped electronic states predicted by theoretical modeling.