nz0c00054_si_001.pdf (2.04 MB)
Surface Ligands for Methylammonium Lead Iodide Films: Surface Coverage, Energetics, and Photovoltaic Performance
journal contribution
posted on 2020-02-18, 15:44 authored by So Min Park, Ashkan Abtahi, Alex M. Boehm, Kenneth R. GrahamSurface
ligand treatment provides a promising approach for passivating
defect states, improving material and device stability, manipulating
interfacial energetics, and improving the performance of perovskite
solar cells (PSCs). To facilitate targeted selection and design of
surface ligands for PSCs, it is necessary to establish relationships
between ligand structure and perovskite surface properties. Herein,
surface ligands with different binding groups are investigated to
determine their extent of surface coverage, whether they form a surface
monolayer or penetrate the perovskite, how they influence material
energetics and photoluminescence, and how this combination of factors
affects PSC performance. Ultraviolet and inverse photoelectron spectroscopy
measurements show that surface ligands can significantly shift the
ionization energy and electron affinity. These changes in surface
energetics substantially impact PSC performance, with the performance
decreasing for ligands that create less favorable energy landscapes
for electron transfer from MAPbI3 to the electron transport
layer, C60.