Are Defects in Lead-Halide Perovskites Healed, Tolerated, or Both?

David Cahen,Leeor Kronik,Gary Hodes

doi:10.1021/acsenergylett.1c02027

Abstract

Are Defects in Lead-Halide Perovskites Healed, Tolerated, or Both?

Highlights

A mong many riddles posed by halide perovskites, the surprising apparent near-absence of harmful defects stands out
This is commonly explained by invoking defect tolerance (DT), but the term is used loosely, sometimes interchangeably with self-healing (SH)
Halide perovskites possess a combination of high-quality average structural order with signif icant dynamic disorder.[2−7] The average structural order fits with the static order of classical semiconductors (e.g., Si, III-V’s, II-VI’s, and ternary semiconductors such as Cu(In,Ga)Se2), but the dynamic disorder is more akin to what occurs in semiconducting organic polymers.[8]

Summary

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A mong many riddles posed by halide perovskites, the surprising apparent near-absence of harmful defects stands out. Some experimental support for a dynamic disorder picture comes from optical measurements of Urbach tail states near the band edges Such measurements have been reported by several groups, and the corresponding Urbach energies were found to be small for polycrystalline films, especially those of MAPI.[58] From the temperature dependence of the Urbach energy, a static disorder component for a polycrystalline MAPI film, smaller than that of any other (single crystal!) semiconductor type, was found, with a high dynamic (temperature-dependent) component.[59] This result is consistent with a low density of average-order, disturbing, static defects.[55,60].

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