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Direct Observation of Crystal Engineering in Perovskite Solar Cells in a Moisture-Free Environment Using Conductive Atomic Force Microscopy and Friction Force Microscopy
journal contribution
posted on 2020-02-25, 19:46 authored by Kunsik An, Seunghyun Rhee, Hyunho Lee, Kyung-Tae Kang, Changhee Lee, Jeonghun KwakThe origin of the increased efficiency of perovskite solar cells
by controlling environmental humidity was investigated using conductive
atomic force microscopy (C-AFM) and friction force microscopy (FFM).
The perovskite thin films fabricated in a humidity-free environment
exhibited better crystallinity and a lower number of trap sites than
the films fabricated in a high-humidity environment. Through in-depth
analysis using C-AFM and FFM, we found that there was a locally decrystallized
area in the perovskite structure fabricated in a high-humidity environment.
By suppressing the local decrystallization in a humidity-free environment,
the power conversion efficiency was increased by about 122%. This
was mainly attributed to the increase in current density as the elimination
of the locally decrystallized area increases the effective active
area. From this perspective, mapping the local current and friction
force using C-AFM and FFM could be new techniques for visualizing
the effect of crystal engineering of perovskite solar cells in a humidity-free
environment.