Stabilizing lead halide perovskites with quaternary ammonium cations: the case of tetramethylammonium lead iodide

Abstract

N(CH3)4PbI3 is much more stable than CH3NH3PbI3, both kinetically and thermodynamically, and much less prone to water-induced degradation; the use of quaternary ammonium cations may be effective to produce more stable lead halide perovskites.

Thermodynamic and Kinetic Aspects of Formamidinium Lead Iodide Thermal Decomposition

“…The thermal behavior of FAPI was studied by either coupling TG/DTA measurements with a quadrupole mass spectrometer (QMS) or comparing the TG/DTA curves with those recently published 38 of tetramethylammonium lead iodide (TMAPI), measured under an inert atmosphere from ambient to 500 °C. The TG/DTA curves coupled with a background-subtracted QMS spectrum of FAPI are shown in Figure 1 .…”

“…The production of one sym-triazine or (HCN) 2 molecule requires the reaction of more than one formamidinium moiety, and this is much more probable to occur in the condensed phase, where their concentration is higher, than in a diluted gaseous phase. Though invisible by XRD, the formation of these species may have a profound effect in the overall value of the E a , requiring the breaking of a stable C–N bond, 38 and in fact, their contribution is clearly visible in the activation energy value obtained by the KAS analysis, which is the sum of all the contributions. In the next section, the analysis of the gas phase performed under effusion (i.e., closer-to-equilibrium) conditions is presented.…”

“…Note that while process 7 involves only a proton exchange among the organic cation and the iodide anion, processes 8 and 9 require the rupture of the C–N bond, which can imply a high activation energy. 38 …”

“…To obtain more accurate pressure values and to estimate the thermodynamic properties of the decomposition reactions, extensive experiments were carried out by the Knudsen effusion mass loss in the 398–487 K temperature range. In this technique, the total pressure P is determined by measuring the mass loss rate Δ m /Δ t provided that the mean molecular weight of the vapor species is independently known: 38 …”

Brightly Luminescent and Moisture Tolerant Phenyl Viologen Lead Iodide Perovskites for Light Emission Applications

“…An alternative approach lies in the use of quaternary ammonium cations, which do not possess acidic protons and consequently eliminate the problem of the Brønsted acidity-related instability. The validity of this approach was demonstrated for tetramethylammonium lead iodide, the simplest quaternary ammonium iodoplumbate (TMPI) . TMPI was found to be more thermodynamically stable than MAPI and completely insensitive to water under ambient conditions .…”