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Understanding the Effect of Lead Iodide Excess on the Performance of Methylammonium Lead Iodide Perovskite Solar Cells
journal contribution
posted on 2022-05-10, 18:04 authored by Zeeshan Ahmad, Rebecca A. Scheidt, Matthew P. Hautzinger, Kai Zhu, Matthew C. Beard, Giulia GalliThe
presence of unreacted lead iodide in organic–inorganic
lead halide perovskite solar cells is widely correlated with an increase
in power conversion efficiency. We investigate the mechanism for this
increase by identifying the role of surfaces and interfaces present
between methylammonium lead iodide perovskite films and excess lead
iodide. We show how type I and II band alignments arising under different
conditions result in either passivation of surface defects or hole
injection. Through first-principles simulations of solid–solid
interfaces, we find that lead iodide captures holes from methylammonium
lead iodide and modulates the formation of defects in the perovskite,
affecting recombination. Using surface-sensitive optical spectroscopy
techniques, such as transient reflectance and time-resolved photoluminescence,
we show how excess lead iodide affects the diffusion and surface recombination
velocity of charge carriers in methylammonium lead iodide films. Our
coupled experimental and theoretical results elucidate the role of
excess lead iodide in perovskite solar cells.
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unreacted lead iodidetheoretical results elucidatepower conversion efficiencymethylammonium lead iodidelead iodide excessexcess lead iodidedifferent conditions resultperovskite solar cellssurface recombination velocityaffecting recombinationusing surfacewidely correlatedtransient reflectanceresolved photoluminescenceprinciples simulationsinterfaces presenthole injectioneither passivationcoupled experimentalcharge carriers
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