Layered 2D perovskites have been extensively investigated by scientists with photovoltaics (PV) expertise due to their good environmental stability. However, a random phase distribution in the perovskite film could affect both the performance and stability of the devices. To overcome this problem, we propose multifunctional interface engineering of 2D GA 2 MA 4 Pb 5 I 16 perovskite by employing guanidinium bromide (GABr) on top of it to optimize the secondary crystallization process. It is found that GABr treatment can facilitate to form a shiny and smooth surface of the 2D GA 2 MA 4 Pb 5 I 16 film with excellent optoelectronic properties. Thus, we realize efficient and stable 2D perovskite solar cells (PSCs) with a champion power conversion efficiency (PCE) of 19.3% under AM 1.5G illumination. Additionally, the optimized device without encapsulation could retain 94% of the initial PCE for more than 3000 h after being stored under ambient conditions.
Longevity is a long‐standing concern for organic–inorganic hybrid perovskite solar cells (PSCs). Recently, the use of low dimensional perovskite has been proven to be a promising strategy to improve the stability of PSCs. Herein, it is demonstrated that 1D perovskitoid based on 2‐diethylaminoethylchloride cations can act as a template to induce 1D@3D perovskite structure, leading to smoother surface texture, longer charge‐carrier lifetime, smaller residual tensile strain, and reduced surface‐defect density in the perovskite film. With this strategy, highly efficient and stable 1D@3D PSC with excellent reproducibility, showing a champion power conversion efficiency (PCE) of 22.9% under standard AM 1.5 G one sun illumination is realized. The unencapsulated optimized devices can retain 94.7%, 92.4%, and 90.0% of their initial PCEs for 2100, 2200, and 2200 h under ambient air, 85 °C and illumination conditions, respectively.
Pure
FAPbI3 (where FA is formamidinium) based perovskite
solar cells (PSCs) have drawn tremendous attention because of their
exceptional photovoltaic properties, although long-term stability
is still a big challenge. Molecular tailoring is one of the practical
approaches to enhancing the stability of FAPbI3 by passivating
the film defects; however, deep understanding of how the molecular
configuration affects the adjacent layer in FAPbI3 PSCs
is urgently needed. Herein, we report a strategy of molecularly tailoring
the FAPbI3/SnO2 interface by employing three
Li salts by varying the anion configurations (CO3
2–, C2O4
2–, and HCOO–). When C–O and C=O groups are in optimal configuration, they
will form the strongest bonds with uncoordinated Sn4+ and
FA+, respectively, which can increase the formation energy
of VFA defects, release the residual stress of the FAPbI3 lattice, facilitate the charge transport at the FAPbI3/SnO2 interface, and improve the stability of the
PSC. Consequently, we obtained a champion device with a power conversion
efficiency of 23.5%, and the unencapsulated device can maintain good
stability under continuous light illumination.
Novel poly(vinyl alcohols) (PVA)
functionalized with pendant thermo- and pH-responsive groups were
prepared by carbonyldiimidazole (CDI)-mediated couplings of N
1,N
1-diethylethane-1,2-diamine
(DEEDA) with controllable modification degree. Nuclear magnetic response
(NMR) and IR have verified the successful modification of PVA. The
macro- and microscopic phase transition behavior of the obtained PVA-DEEDA-t (t = 10, 30, 70, and 90 h) was thoroughly
characterized using various techniques, including turbidity measurement,
NMR, and dynamic light scattering (DLS). PVA-DEEDA-t is demonstrated to possess tunable lower critical solution temperature
(LCST) between 58 and 24 °C. LCST is dependent on solution pH
and degree of PVA modification (14.1–20.9%). By combining DLS
and DOSY characterizations, it can be concluded that both coil-to-globule
transition and aggregation occurred to PVA-DEEDA-t during phase transition, while only coil-to-globule transition can
be detected for the pristine PVA. 2D NOESY proved that the −NH–
segment on PVA-DEEDA-t is in close (<5 Å)
proximity to the main chain of PVA, as evidenced by the appearance
of NOE signal between −NH– on DEEDA and −CH2–CH– chain of PVA when the temperature increased
above LCST. To exploit the functional applications, the PVA-DEEDA-90
h was transformed into gel and film forms. PVA-DEEDA-90 h gel obtained
by adding borax enabled controlled drug (e.g., RhB) release due to
its temperature- and pH-dependent permeability. The PVA-DEEDA-90 h
film was also casted on ITO glass, creating a smart surface with tunable
wettability and interfacial ion transportation with high sensitivity
toward the pH and temperature.
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