Bandlike Transport and Charge-Carrier Dynamics in BiOI Films.
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Following the emergence of lead halide perovskites (LHPs) as materials for efficient solar cells, research has progressed to explore stable, abundant, and nontoxic alternatives. However, the performance of such lead-free perovskite-inspired materials (PIMs) still lags significantly behind that of their LHP counterparts. For bismuth-based PIMs, one significant reason is a frequently observed ultrafast charge-carrier localization (or self-trapping), which imposes a fundamental limit on long-range mobility. Here we report the terahertz (THz) photoconductivity dynamics in thin films of BiOI and demonstrate a lack of such self-trapping, with good charge-carrier mobility, reaching ∼3 cm2 V-1 s-1 at 295 K and increasing gradually to ∼13 cm2 V-1 s-1 at 5 K, indicative of prevailing bandlike transport. Using a combination of transient photoluminescence and THz- and microwave-conductivity spectroscopy, we further investigate charge-carrier recombination processes, revealing charge-specific trapping of electrons at defects in BiOI over nanoseconds and low bimolecular band-to-band recombination. Subject to the development of passivation protocols, BiOI thus emerges as a superior light-harvesting semiconductor among the family of bismuth-based semiconductors.
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Engineering and Physical Sciences Research Council (EP/S004947/1)
Engineering and Physical Sciences Research Council (EP/V010840/1)
Engineering and Physical Sciences Research Council (EP/V014498/2)
Royal Academy of Engineering (RF\201718\1701)
Institute for Advanced Study, Technische Universit?t M?nchen (NA)