Unusual polarization-insensitive negative photoresponse of chiral double perovskite ( R/ S-MBA) 4AgBiI 8

Le résumé fourni par la source

Traditional perovskite single crystals typically exhibit polarization-dependent photoresponse characteristics due to crystallographic anisotropy, particularly showing sensitivity to linearly polarized light (LP), and to left/right circularly polarized light (CPL) in chiral perovskites. However, achieving complete linear- and circular-polarization insensitivity in single perovskite crystals with intrinsic structural anisotropy remains an unresolved challenge. This study presents the observation of an unusual linear/circular-polarization-insensitive negative photoresponse in two-dimensional (2D) structured chiral lead-free double perovskite (R/S-MBA)4AgBiI8 single crystals. These crystals were prepared by a method combining cyclic heating and slow cooling processes. They have a defect density as low as 8.01×109 cm-3 and a chiroptical anisotropy factor gCD of 1.5×10-3. Mechanistic investigations through Density Functional Theory (DFT) calculation, temperature dependent fluorescence spectroscopy and Raman spectroscopy attribute this anomaly to strong exciton self-trapping effects (STE), where photo-generated excitons form stable localized trapped states, dominating charge transport and effectively masking the polarization sensitivity. This discovery provides new insights into the structure-property relationship of perovskite materials and suggests potential pathways for designing novel polarization-insensitive optoelectronic devices.

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