Perovskite
solar cells (PSCs) have reached certified efficiencies
of up to 23.7% but suffered from frailness and instability when exposed
to ambient atmosphere. Zinc oxide (ZnO), when used as electron transport
layer (ETL) on PSCs, gives rise to excellent electronic, optic, and
photonic properties, yet the Lewis basic nature of ZnO surface leads
to deprotonation of the perovskite layer, resulting in serious degradation
of PSCs using ZnO as ETL. Here, we report a simple but effective strategy
to convert ZnO surface into ZnS at the ZnO/perovskite interface by
sulfidation. The sulfide on ZnO–ZnS surface binds strongly
with Pb2+ and creates a novel pathway of electron transport
to accelerate electron transfer and reduce interfacial charge recombination,
yielding a champion efficiency of 20.7% with improved stability and
no appreciable hysteresis. The model devices modified with sulfide
maintained 88% of their initial performance for 1000 h under storage
condition and 87% for 500 h under UV radiation. ZnS is demonstrated
to act as both a cascade ETL and a passivating layer for enhancing
the performance of PSCs.
Perovskite
films prepared with CH3NH2 molecules
under ambient conditions have led to rapid fabrication of perovskite
solar cells (PSCs), but there remains a lack of mechanistic studies
and inconsistencies with operability in their production. Here the
crystal structure of CH3NH2–CH3NH3PbI3 was analyzed to involve hydrogen bonds
(CH3NH2···CH3NH3
+) and has guided the facile, reproducible preparation
of high-quality perovskite films under ambient conditions. Hydrogen
bonds within CH3NH2···CH3NH3
+ dimers were found in the CH3NH2–CH3NH3PbI3 intermediates, accompanied by 1D-PbI3
– chains (δ-phase). The weakly hydrogen-bonded CH3NH2 molecules were easily released from the CH3NH2–CH3NH3PbI3 intermediates, contributing to rapid, spontaneous phase transition
from 1D-PbI3
– (δ-phase) to 3D-PbI3
– (α-phase). Further introduction
of CH3NH3Cl into the CH3NH2–CH3NH3PbI3 intermediates
led to interruption of 1D-PbI3
– transition
into 0D-Pb2I9‑x
Cl
x
5–(0 < x < 6), adjusting the phase transition route toward 3D-PbI3
–. On the basis of the above understanding,
CH3NH2 solution in ethanol and CH3NH3Cl were used for precursors and a best efficiency of
20.3% in PSCs was achieved. Large-scale modules (12 cm2 aperture area) fabricated by a dip-coating technology exhibited
an efficiency up to 16.0% and outstanding stability over 10 000
s under continuous output. The developed preparation method of perovskite
precursors and insightful research into the methylamine-dimer-induced
phase transition mechanism have enabled the production of high-quality
perovskite films with robust operability, showing great potential
for large-scale commercialization.
An organic-inorganic hybrid electrolyte based on a cyclic Ti-oxo cluster as the inorganic core and naphthalenebased organic ammonium bromide salts as the electrolyte was developed with easy synthesis and low cost. The new hybrid electrolyte exhibits excellent solubility in methanol, aligned work function, good conductivity, and amorphous state in thin film, enabling its successful application as a cathode interlayer in organic solar cells with a high power conversion efficiency of 17.19 %. This work demonstrates that the hybrid electrolytes are a new kind of semiconductor, exhibiting promising applications in organic electronics.
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