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A highly emissive surface layer in mixed‐halide multication perovskites

DOI: 10.1002/adma.201902374 DOI Help

Authors: Zahra Andaji-garmaroudi (University of Cambridge) , Mojtaba Abdi-jalebi (University of Cambridge) , Dengyang Guo (Delft University of Technology) , Stuart Macpherson (University of Cambridge) , Aditya Sadhanala (University of Cambridge) , Elizabeth M. Tennyson (University of Cambridge) , Edoardo Ruggeri (University of Cambridge) , Miguel Anaya (University of Cambridge) , Krzysztof Galkowski (University of Cambridge) , Ravichandran Shivanna (University of Cambridge) , Kilian Lohmann (University of Cambridge) , Kyle Frohna (University of Cambridge) , Sebastian Mackowski (Nicolaus Copernicus University) , Tom J. Savenije (Delft University of Technology) , Richard H. Friend (University of Cambridge) , Samuel D. Stranks (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Materials

State: Published (Approved)
Published: September 2019
Diamond Proposal Number(s): 17223

Open Access Open Access

Abstract: 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.

Journal Keywords: halide perovskites; luminescence; passivation; photoinduced ion migration; time‐resolved spectroscopy

Subject Areas: Materials


Instruments: I07-Surface & interface diffraction

Documents:
Andaji-Garmaroudi.pdf