Surface
passivation by various organic molecules is a widely used
approach to compensate surface defects and to improve a stability
of hybrid halide perovskites. For commonly used cationic passivators,
the formation of 2D phases and related heterostructures is considered
as an essential part of the passivation process. However, there is
an intriguing fundamental question: is it possible to achieve effective
and stable passivation by the thinnest possible layer? In this article,
we applied an iodide salt of a new bulky bifunctional 11-carboxy-decylammonium
cation (further AUDA+) as a passivator which can not only
passivate both VI
• and VMA
′ defects but can also expectedly form on the 3D perovskite surface
a dense and stable “monolayer” assembled due to the
strong hydrogen bonds between the terminal carboxylic groups and,
hereby, suppressing the passivator migration in the bulk of the perovskite.
Applying a wide set of methods such as steady-state and time-resolved
photoluminescence spectroscopy, X-ray diffraction, and scanning electron
microscopy, we revealed that the passivation regime could be controlled
by adjustment of two treatment parametersthe concentration
of AUDA+I– and the post-annealing temperature
resulting in either the formation of 2D/3D heterostructures or surface
defect passivation by the “monolayer” without the formation
of additional phases. The “monolayer” regime was found
to provide a greater improvement of optical properties: photoluminescence
intensity and average charge carrier lifetime increase by 10 and 2.5
times, respectively, and demonstrate significantly better properties
after long-time light soaking. These results indicate that a fine
tuning of passivation conditions provides a significant increase in
photostability even without formation of a 2D capping layer, thus
revealing new possibilities to enhance perovskite solar cells’
lifetime.
Organic diammonium cations are a promising component of both layered (2D) and conventional (3D) hybrid halide perovskites in terms of increasing the stability of perovskite solar cells (PSCs). We investigated the crystallization ability of phase-pure 2D perovskites based on 1,4-butanediammonium iodide (BDAI2) with the layer thicknesses n = 1, 2, 3 and, for the first time, revealed the presence of a persistent barrier to obtain BDA-based layered compounds with n > 1. Secondly, we introduced BDAI2 salt into 3D lead–iodide perovskites with different cation compositions and discovered a threshold-like nonmonotonic dependence of the perovskite microstructure, optoelectronic properties, and device performance on the amount of diammonium additive. The value of the threshold amount of BDAI2 was found to be ≤1%, below which bulk passivation plays the positive effect on charge carrier lifetimes, fraction of radiative recombination, and PSCs power conversion efficiencies (PCE). In contrast, the presence of any amount of diammonium salt leads to the sufficient enhancement of the photothermal stability of perovskite materials and devices, compared to the reference samples. The performance of all the passivated devices remained within the range of 50 to 80% of the initial PCE after 400 h of continuous 1 sun irradiation with a stabilized temperature of 65 °C, while the performance of the control devices deteriorated after 170 h of the experiment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.