Hybrid organic–inorganic CH₃NH₃PbI₃perovskite building blocks: Revealing ultra‐strong hydrogen bonding and mulliken inner complexes and their implications in materials design

Abstract

Methylammonium lead iodide (CH NH PbI ) perovskite compound has produced a remarkable breakthrough in the photovoltaic history of solar cell technology because of its outstanding device-based performance as a light-harvesting semiconductor. Whereas the experimental and theoretical studies of this system in the solid state have been numerously reported in the last 4 years, its fundamental cluster physics is yet to be exploited. To this end, this study has performed theoretical investigations using DFT-M06-2X/ADZP to examine the principal geometrical, electronic, topological, and orbital properties of the CH NH PbI molecular building block. The intermolecular hydrogen bonded interactions examined for the most important conformers of the system are found to be unusually strong, with binding energies lying between -93.53 and -125.11 kcal mol (beyond the covalent limit, -40 kcal mol ), enabling us to classify the underlying interactions as ultra-strong type since their characteristic properties are unidentical with those have already been proposed as very strong, strong, moderate, weak, and van der Waals. Based on this, together with the unusually high charge transfers, strong hyperconjugative interactions, sophisticated topologies of the charge density, and short intermolecular distances of separation, we have characterized the conformers of CH NH PbI as Mulliken inner complexes. The consequences of these, as well as of the ultra-strong interactions, in designing novel functional nanomaterials are outlined. © 2017 Wiley Periodicals, Inc.

Halogen in materials design: Fluoroammonium lead triiodide (FNH3PbI3) perovskite as a newly discovered dynamical bandgap semiconductor in 3D

“…These results demonstrate that the molecular blocks with shortest intermolecular contact distances are accompanied with strongest energy of interaction between the B‐ and Y‐site ions. The energy strengths for these noncovalent interactions are in line with those discussed previously for analogous perovskite systems …”

“…This might be understandable since the binding energy for this binary complex in (C) is evaluated to be as large as −79.42 kcal mol −1 (−3.444 eV). Note that noncovalent binding energies similar strengths have been reported elsewhere …”

“…This may mean that the long I•••F(N) distance might not be characterized as a consequence of any noncovalent interaction. However, our binding energy calculation suggests that the Δ E (BSSE) for this binary complex to be −64.98 kcal mol −1 (−2.818 eV), which is much more (∼260 times) greater than an ordinary van der Waals interaction (–0.25 kcal mol −1 ) . This suggests that the I•••FN intermolecular interactions, albeit long‐ranged, might not be unrealistic.…”

“…One of the crucial features in the design of hybrid perovskite compounds lies in the understanding of the nature of intermolecular interactions. These play a vital role not only in determining the overall geometry but also for the emergence of desirable materials properties such as small carrier masses and others . We have identified a variety of intermolecular noncovalently bonded synthons that cooperate each other to stabilize the studied polymorphs of FNH 3 PbI 3 .…”

“…These may or may not comprise the lead content . These can be either all‐inorganic, or a mixture of an organic moiety with an inorganic one (organic–inorganic), or metal‐organic hybrids . A critical aspect of some of these perovskites lies in the “direct‐to‐indirect/indirect‐to‐direct” nature of their bandgap .…”