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Title: Why lead-halide perovskites keep long carrier lifetimes despite defects
Plain: Solution-made perovskite films have many defects, yet light-generated charges in them survive for millionths of a second, much longer than in comparably imperfect ordinary semiconductors. Proposed reasons include charges wrapped in lattice distortions (polarons), a constantly fluctuating lattice, and defects whose energy levels lie harmlessly near the band edges.
Precise: In MAPbI3, FAPbI3 and CsPbBr3, nonradiative lifetimes reach about 1e-6 s at trap densities of order $1e15\ \text{to}\ 1e16\,\mathrm{cm}^{-3}$ despite modest mobilities. Determine which mechanism dominates the suppression of Shockley-Read-Hall (defect-mediated) recombination: shallow intrinsic defect levels from antibonding valence-band character, large-polaron screening of capture, dynamic disorder reducing capture cross sections, or spin-split (Rashba) band edges. An answer is a ranking of mechanisms with first-principles nonadiabatic capture rates matching measured lifetimes versus $T$ and composition.
Settled by: Computed capture coefficients for the dominant defects, including anharmonic lattice dynamics, that reproduce measured lifetimes and their temperature dependence.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: contested
Status note: (empty)
Posed since: (empty)