posted on 2021-10-13, 14:44authored byAmalraj Peter Amalathas, Lucie Landová, Katarína Ridzoňová, Lukáš Horák, Pavla Bauerová, Jakub Holovský
The
morphological bulk defects and trap sites between TiO2 and
the perovskite layer are critical issues in charge separation
and electron transport. In this study, an effective method for improving
the mesoporous TiO2/perovskite interfacial characteristics
in perovskite solar cells (PSCs) is demonstrated by modifying mesoporous
TiO2 with potassium (K) treatment. It is found that the
modification of mesoporous TiO2 with the K treatment enhances
the perovskite crystallization process, producing a perovskite film
with higher crystallinity and larger grain sizes. It is also found
that the K treatment not only effectively passivates the trap sites
in mesoporous TiO2 but also reduces the sub-band-gap deep
defect states at the interface of the perovskite, as revealed by photothermal
deflection spectroscopy, thereby suppressing the nonradiative recombination
and improving the Voc of the PSCs. Moreover,
stronger photoluminescence quenching and shorter carrier lifetime
are observed for the perovskite on K-treated mesoporous TiO2, indicating more efficient charge collection across the interface.
As a result of these advancements, the PSC based on K-treated mesoporous
TiO2 shows a high power conversion efficiency of 20.60%
compared to the PSC without the K treatment (18.17%) and also significantly
improves the environmental stability in ambient air.