Strain-activated light-induced halide segregation in mixed-halide perovskite solids.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33303755.
- Also identified by DOI 10.1038/s41467-020-20066-7 and PMC identifier 7730187.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Light-induced halide segregation limits the bandgap tunability of mixed-halide perovskites for tandem photovoltaics. Here we report that light-induced halide segregation is strain-activated in MAPb(I<sub>1-x</sub>Br<sub>x</sub>)<sub>3</sub> with Br concentration below approximately 50%, while it is intrinsic for Br concentration over approximately 50%. Free-standing single crystals of CH<sub>3</sub>NH<sub>3</sub>Pb(I<sub>0.65</sub>Br<sub>0.35</sub>)<sub>3</sub> (35%Br) do not show halide segregation until uniaxial pressure is applied. Besides, 35%Br single crystals grown on lattice-mismatched substrates (e.g. single-crystal CaF<sub>2</sub>) show inhomogeneous segregation due to heterogenous strain distribution. Through scanning probe microscopy, the above findings are successfully translated to polycrystalline thin films. For 35%Br thin films, halide segregation selectively occurs at grain boundaries due to localized strain at the boundaries; yet for 65%Br films, halide segregation occurs in the whole layer. We close by demonstrating that only the strain-activated halide segregation (35%Br/45%Br thin films) could be suppressed if the strain is properly released via additives (e.g. KI) or ideal substrates (e.g. SiO<sub>2</sub>).