Enhancing High Humidity Stability of Quasi‐2D Perovskite Thin Films through Mixed Cation Doping and Solvent Engineering

Abstract

Perovskite materials show excellent photovoltaic performance along with simple processing and low‐energy requirements. Despite their high power conversion efficiency (PCE), instability in the presence of moisture is still a major challenge. An effective method to enhance perovskite stability is by reducing dimensionality through incorporation of long organic cations into the perovskite crystal, which improves charge‐carrier extraction efficiency of the perovskites compared to conventional 3D perovskites. Quasi‐2D perovskites or 2D/3D perovskites strike a good balance between PCE and stability, having much improved stability compared to 3D structures while retaining excellent optoelectronic properties. Yielding better thermal stability and broader absorption into the near‐infrared, formamidinium iodide (FAI) doping has positive influences yet tends to cause poor surface morphology. Here, we introduce highly stable MA/FA‐based quasi‐2D perovskite fabricated by mixed cation doping (MCD), which is repeated deposition of MA and FA cations onto a quasi‐2D perovskite layer. MCD enables better morphology and surface passivation, leading to fewer defects. MA/FA‐based quasi‐2D perovskite with quasi‐cubic structure has high humidity resistivity, remaining intact after 90 days under 60% relative humidity without encapsulation. The underlying mechanism is further explained by binding and formation energies of cation mixture in solution and perovskite structure through computational analysis.

Polymer‐Based Anti‐Solvent Engineering to Fabricate Stable and Efficient Triple‐Cation Perovskite Solar Cells

“…Several techniques have been utilized to fabricate a high‐quality perovskites film with less impurities phases and defects. Many fabrication approaches have used, include one‐step deposition, sequential spin‐coating, flash infrared annealing, etc., [,10d] Since its introduction in 2015, the anti‐solvent approach has been well‐used for one‐step fabrication and has become an universal way for depositing a highly crystalline perovskite [11] . The anti‐solvent approach allows quick nucleation for subsequent grain development, resulting in continuous and uniform layer after rapid heat treatment [12] .…”

Phase-Pure Layered Perovskite Films for Photodetectors with Enhanced Performance and Stability

“…The improved stability under light illumination in the phase-pure layered perovskite is possibly because the suppression of nonradiative recombination is beneficial for overcoming heat generation/dissipation . Moreover, the DCM-treated phase-pure perovskite shows better long-term stability under ambient conditions, as its compact morphology may help in preventing the penetration of water/oxygen in air. − As shown in Figure c, the color of the DCM-treated film shows no obvious change after 30 days, while the as-cast film degrades into a yellowish color of the PbI 2 precursor (Figure S11). Hence, there is no surprise that the photoresponsivity of the as-cast device drops below 50% and the unencapsulated device based on the DCM-treated film is still robust after exposure to an ambient environment, as shown in Figure d.…”

Scale-up Solutions of 2D Perovskite Photovoltaics: Insights of Multiscale Structures

“…Substances present in the inks or involved in the processing can affect the band edge alignment for both the 2D/3D heterojunction (Figure b) and the perovskite/substrate interface. , Thus, it becomes necessary to establish a clear relationship between strain and dipole effects on the surface and interface, induced by the collective and fine moieties present. Fortunately, recent research has achieved success in connecting the interface dipoles, work functions, and valence band alignments in 3D, 2D perovskite surfaces/interfaces and their heterostructures .…”