B
B9
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Defect-Mediated Electron-Phonon Coupling in Halide Double Perovskites
How intrinsic point defects in lead-free halide double perovskites (Cs2AgInCl6, Cs2NaInCl6) create mid-gap electronic states that couple to lattice phonons. The learner sees how this coupling reveals itself as a Fano asymmetry in the lowest-frequency Raman phonon mode plus a sub-bandgap photoluminescence band, both present only in defect-rich micron-sized crystals and tunable by the crystal-growth method, and how the coupling strength evolves with temperature away from the anharmonic phonon trend.