Formamide iodide: a new cation additive for inhibiting δ-phase formation of formamidinium lead iodide perovskite

Abstract

Perovskite solar cells (PSCs) employing organic-inorganic hybrid lead perovskite have attracted much attention as promising next generation solar cells because of their low fabrication cost and extremely high power conversion...

Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

“…However, the interactions with the Pb-X cage seem to have significant destabilization effect, which is also reflected in the lack of reports concerning the attainability of these particular perovskites. Concerning the group pf FM, HA, HZ, our calculations indicate that FM mixtures are statistically the worst candidates, already signaled by the absence of the 3D phase in [36], followed by HA and HZ. However, in the case of HZ, surprisingly, mixtures with large proportions of MA or EA yield rather undistorted structures.…”

“…A more detailed analysis can take into account structural properties of the cations and alternative definitions, e.g., the globularity factor [33] may be introduced. [36].…”

“…Besides the MAPbX 3 compounds, the synthesis of single-cation perovskites has been reported for FAPbI 3 [39], EAPbI 3 [40], GAPbI 3 [41]. In contrast, a recent study indicates that FM was not successfully embedded in the perovskite structure, but rather it was included as an additive [36], despite the similarity with the FA cation. The pure usage of HA cations yields structures with face-sharing octahedra that differ from the standard, corner-sharing perovskites [37].…”

Phase‐Pure Engineering for Efficient and Stable Formamidinium‐Based Perovskite Solar Cells

“…Introducing various functional materials into FAPbI 3 films would be beneficial for stabilizing the phase-pure α-FAPbI 3 , including popular additive engineering, interfacial engineering, solvent engineering, and dimensional engineering. [27][28][29][30][43][44][45][46][146][147][148] The passivation mechanism of these passivators for perovskite is extremely important to look for an appropriate and effective passivator. To passivate Pb 2þ , we can look for functional materials with lone-pair-electron Lewis bases to form Lewis acid-base adducts with the undercoordinated Pb 2þ .…”

“…In addition, a variety of organic ammonium cations were studied to prepare pure α‐FAPbI 3 , including formamide cation (FoA + ) that forms an adduct with PbI 2 to improve the solubility of PbI 2 and promote the crystal growth of perovskite films and long alkyl chain‐containing imidazolium‐based ionic liquids that are used as the additive to improve the humidity resistance and reduce the defect density of FAPbI 3 PSCs, such as 1‐hexyl‐3‐methylimidazolium iodide (HMII)‐based ionic liquid, polyfluoroalkylated imidazolium 1‐methyl‐3‐(3′,3′,4′,4′,4′‐pentafluorobutyl)imidazolium tetrafluoroborate (MFIM‐2). [ 148,167,168 ] All these modified devices suppressed the formation of yellow phase and showed better photovoltaic performance.…”