The use of molecular modulators to
reduce the defect density at
the surface and grain boundaries of perovskite materials has been
demonstrated to be an effective approach to enhance the photovoltaic
performance and device stability of perovskite solar cells. Herein,
we employ crown ethers to modulate perovskite films, affording passivation
of undercoordinated surface defects. This interaction has been elucidated
by solid-state nuclear magnetic resonance and density functional theory
calculations. The crown ether hosts induce the formation of host–guest
complexes on the surface of the perovskite films, which reduces the
concentration of surface electronic defects and suppresses nonradiative
recombination by 40%, while minimizing moisture permeation. As a result,
we achieved substantially improved photovoltaic performance with power
conversion efficiencies exceeding 23%, accompanied by enhanced stability
under ambient and operational conditions. This work opens a new avenue
to improve the performance and stability of perovskite-based optoelectronic
devices through supramolecular chemistry.
Formamidinium lead iodide perovskites are promising light-harvesting materials, yet stabilizing them under operating conditions without compromising optimal optoelectronic properties remains challenging. We report a multimodal host–guest complexation strategy to overcome this challenge using a crown ether, dibenzo-21-crown-7, which acts as a vehicle that assembles at the interface and delivers Cs+ ions into the interior while modulating the material. This provides a local gradient of doping at the nanoscale that assists in photoinduced charge separation while passivating surface and bulk defects, stabilizing the perovskite phase through a synergistic effect of the host, guest, and host–guest complex. The resulting solar cells show power conversion efficiencies exceeding 24% and enhanced operational stability, maintaining over 95% of their performance without encapsulation for 500 h under continuous operation. Moreover, the host contributes to binding lead ions, reducing their environmental impact. This supramolecular strategy illustrates the broad implications of host–guest chemistry in photovoltaics.
Cost management and toxic waste generation are two key issues that must be addressed before the commercialization of perovskite optoelectronic devices. We report a groundbreaking strategy for eco-friendly and cost-effective fabrication of highly efficient perovskite solar cells. This strategy involves the usage of a high volatility co-solvent, which dilutes perovskite precursors to a lower concentration (<0.5 M) while retaining similar film quality and device performance as a high concentration (>1.4 M) solution. More than 70% of toxic waste and material cost can be reduced. Mechanistic insights reveal ultra-rapid evaporation of the co-solvent together with beneficial alteration of the precursor colloidal chemistry upon dilution with co-solvent, which in-situ studies and theoretical simulations confirm. The co-solvent tuned precursor colloidal properties also contribute to the enhancement of the stability of precursor solution, which extends its processing window thus minimizing the waste. This strategy is universally successful across different perovskite compositions, and scales from small devices to large-scale modules using industrial spin-coating, potentially easing the lab-to-fab translation of perovskite technologies.
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