A Highly Emissive Surface Layer in Mixed-Halide Multication Perovskites

Zahra Andaji-Garmaroudi, Mojtaba Abdi-Jalebi, Dengyang Guo, Stuart Macpherson, Aditya Sadhanala, Elizabeth M. Tennyson, Edoardo Ruggeri, Miguel Anaya, Tom J. Savenije, More Authors

Research output: Contribution to journalArticleScientificpeer-review

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Mixed-halide lead perovskites have attracted significant attention in the field of photovoltaics and other optoelectronic applications due to their promising bandgap tunability and device performance. Here, the changes in photoluminescence and photoconductance of solution-processed triple-cation mixed-halide (Cs0.06MA0.15FA0.79)Pb(Br0.4I0.6)3 perovskite films (MA: methylammonium, FA: formamidinium) are studied under solar-equivalent illumination. It is found that the illumination leads to localized surface sites of iodide-rich perovskite intermixed with passivating PbI2 material. Time- and spectrally resolved photoluminescence measurements reveal that photoexcited charges efficiently transfer to the passivated iodide-rich perovskite surface layer, leading to high local carrier densities on these sites. The carriers on this surface layer therefore recombine with a high radiative efficiency, with the photoluminescence quantum efficiency of the film under solar excitation densities increasing from 3% to over 45%. At higher excitation densities, nonradiative Auger recombination starts to dominate due to the extremely high concentration of charges on the surface layer. This work reveals new insight into phase segregation of mixed-halide mixed-cation perovskites, as well as routes to highly luminescent films by controlling charge density and transfer in novel device structures.

Original languageEnglish
Article number1902374
Number of pages9
JournalAdvanced Materials
Issue number42
Publication statusPublished - 2019


  • halide perovskites
  • luminescence
  • passivation
  • photoinduced ion migration
  • time-resolved spectroscopy


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