Halide Perovskites: A Platform for ‘Defect-tolerance’ and ‘Self-healing’

In recent years, halide perovskites (HaPs) have taken what seems to be a unique place among functional semiconductors – at the bulk and the nanoscale – surpassing expectations and surprising many materials researchers. An often-asked question is: what may be the reason(s) that HaPs performance gets close to that of high-quality optoelectronic semiconductors, although their fabrication can be similar to that of the organic electronic materials which, though, are of considerably lower semiconductor quality? As ‘high quality’ refers (here) to ‘low density of defects/traps that are optical or electronically active’ (the defect density of HaPs is ~10¹⁰ cm^-3 in single crystals and < ~10¹⁶ cm^-3 in polycrystalline films),¹ ‘defect-tolerance’ and ‘self-healing’ have been proposed as possible explanations. These will give rise to an effectively reduced optoelectronically relevant defect density.

To support the ‘defect tolerance’ and ‘self-healing’ hypothesis, I will present experimental evidence that strongly supports the idea that HaPs (not limited to the commonly used APb(I,Br)₃ compounds) are a platform for both ‘defect tolerance’ and ‘self-healing’, both physically and chemically. The ‘physical’ part includes an experimental analysis of the ‘deformation potential’, which makes ‘defect tolerance’ very probable, both due to its absolute value and algebraic sign. The ‘chemical’ part includes assembly of evidence that supports recyclability of degradation products back to the starting material, which means a path for ‘self-healing’ back to a perovskite structure.² New experimental evidence, via comparison of novel chemically synthesized AX₃ compounds with the perovskite APbX₃ compounds, support a chemical path for self-defect passivation.³

1. Brenner, T. M., Egger, D. A., et al. Nat. Rev. Mater. 16011 (2016).
2. Ceratti D. R. et al. Adv. Mater. 30, 1706273 (2018).
3. Walsh, A. & Zunger, A. Nat. Mater. 16, 964 (2017).