Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films.
We perform scanning microwave microscopy (SMM) to study the spatially varying electronic properties and related morphology of pristine and degraded methylammonium lead-halide (MAPI) perovskite films fabricated under different ambient humidity. We find that higher processing humidity leads to the emergence of increased conductivity at the grain boundaries but also correlates with the appearance of resistive grains that contain PbI2. Deteriorated films show larger and increasingly insulating grain boundaries as well as spatially localized regions of reduced conductivity within grains. These results suggest that while humidity during film fabrication primarily benefits device properties due to the passivation of traps at the grain boundaries and self-doping, it also results in the emergence of PbI2-containing grains. We further establish that MAPI film deterioration under ambient conditions proceeds via the spatially localized breakdown of film conductivity, both at grain boundaries and within grains, due to local variations in susceptibility to deterioration. These results confirm that PbI2has both beneficial and adverse effects on device performance and provide new means for device optimization by revealing spatial variations in sample conductivity as well as morphological differences in resistance to sample deterioration.
National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
Samuel
0000-0002-4073-5322
S
Berweger
National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
Gordon A
GA
MacDonald
National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
Mengjin
M
Yang
National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
Kevin J
KJ
Coakley
National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
Joseph J
JJ
Berry
National Renewable Energy Laboratory , Golden, Colorado 80401, United States.
Kai
K
Zhu
National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
Frank W
FW
DelRio
National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
Thomas M
TM
Wallis
National Institute of Standards and Technology , Boulder, Colorado 80305, United States.
Pavel
P
Kabos
atomic force microscope; microwave; near-field; perovskite; photovoltaic