Optical Properties of Layered Hybrid Organic–Inorganic Halide Perovskites: A Tight-Binding GW-BSE Study

Abstract

We present a many-body calculation of the band structure and optical spectrum of the layered hybrid organicinorganic halide perovskites in the Ruddlesden-Popper phase with the general formula A 2 A n−1 M n X 3n+1 , focusing specifically on the lead iodide family. We calculate the mean-field band structure with spin-orbit coupling, quasiparticle corrections within the GW approximation, and optical spectra using the Bethe-Salpeter equation. The model is parameterized by first-principles calculations and classical electrostatic screening, enabling an accurate but cost-effective study of large unit cells and corresponding thickness-dependent properties. A transition of the electronic and optical properties from quasi-two-dimensional behavior to three-dimensional behavior is shown for increasing n and the nonhydrogenic character of the excitonic Rydberg series is analyzed. The thickness-dependent 1s and 2s exciton energy levels are in good agreement with recently reported experiments and the 1s exciton binding energy is calculated to be 302 meV for n = 1, 97 meV for n = 5, and 37 meV for n = ∞ (bulk MAPbI 3 ).Hybrid organic-inorganic perovskites (HOIPs) are promising photovoltaic materials, most recently showing a high power conversion efficiency of over 24%. 1 A three dimensional bulk HOIP AMX 3 can be transformed into a layered HOIP in the Ruddlesden-Popper phase A 2 A n−1 M n X 3n+1 by substituting a small organic cation A + by a bulkier one A + .Common choices for the small organic cation are A + =CH 3 NH + 3 , NH + 4 ; for the bulkier cation are A + =C 4 H 9 NH + 3 , C 6 H 5 C 2 H 4 NH + 3 ; for the metal are M 2+ =Sn 2+ , Pb 2+ ; and for the halide are X − =Cl − , I − , Br − . A major drawback of the 3D HOIPs for photovoltaics is their relatively fast degradation when exposed to air, moisture, and light; in contrast, the layered HOIPs are more stable while maintaining high power conversion efficiencies under working conditions. 2,3 The optical properties of layered HOIPs can also be easily controlled by composition, 4 enhancing their flexibility for a variety of optoelectronic applications. Unlike the van der Waals materials -a prototypical family of layered materials including graphene, hexagonal boron nitride, and the transition-metal dichalcogenides -the layered HOIPs have sublayers that are covalently bonded. This distinct property makes the layered HOIPs an insightful mixeddimensional platform for investigating the transition of optoelectronic properties from two dimensional to three dimensional.The n-dependent properties of layered HOIPs have been experimentally investigated, especially during the last five years, 5-9 including mechanically exfoliated thin sheets of a layered HOIP. 10,11 Early theoretical investigations of the optical properties of layered HOIPs were performed using the effective mass approximation, giving good estimates for the exciton binding energy and a qualitative explanation of the essential physics. 5,12-14 For a quantitative analysis, ab initio approaches such as density functional...

Anisotropic 2D excitons unveiled in organic–inorganic quantum wells

“…Building on past calculations, [29][30][31] our results are broadly consistent with prior work on related classes of hybrid and low-dimensional materials, layered halide perovskites 11 and of 2D transition metal chalcogenide semiconductors, where model calculations 9,10 have provided a detailed framework for understanding measurements of strongly-bound and confined excitons. Our ab initio GW-BSE calculations capture the inhomogeneous and anisotropic nature of the optical absorption, dielectric screening, and electron-hole interaction in this complex layered hybrid material, yielding good agreement with experiment, without resorting to simplifications or empirical approximations, paving the way for future ab initio GW-BSE work on hybrid chalcogenide systems like [AgSePh] N , layered perovskite systems, and beyond.…”

“…We note the transformation matrix between primitive and conventional unit cells is [ optimized norm-conserving pseudopotentials (http://www. quantum-simulation.org/potentials/sg15_oncv/), including the following valence states: Ag -5s(1), 4d(10), 4p(6), 4s(2); Se -4s(2), 4p(4), 3d (10). For quasiparticle excitations and band structure, we perform a one-shot G 0 W 0 43 calculation from a PBE starting point, using the BerkeleyGW code 44 within the generalized plasmon-pole model.…”

“…4 A large exciton binding energy may allow to harness Bose-Einstein statistics at room temperature, with deep implications for both fundamental and applied science. 5,6 Two dimensional (2D) transition metal dichalcogenides (TMDs) 7 and 2D perovskites [8][9][10][11] have emerged as a focal point for many recent photophysical studies. Here, we expand the field of materials supporting strongly bound and tuneable excitonic resonances to hybrid organic-inorganic polymer systems based on metal-chalcogenide layers spaced by phenyl groups.…”

Observation of Two Thresholds Leading to Polariton Condensation in 2D Hybrid Perovskites

“…In the last decade, hybrid organic-inorganic 2D perovskites have attracted considerable interest because of their intriguing optical properties [1,2,3] and better moisture stability than their bulk counterpart [4] . In particular, these materials show a natural quantum well-like structure formed by an inorganic layer of (PbX6) 2 − octahedra (in which X is an halogen), sandwiched between bilayers of intercalated alkylammonium cations.…”

High‐throughput computational design of halide perovskites and beyond for optoelectronics

“…ε 1 (ω) and ε 2 (ω) can be calculated from ground-state electronic structure calculations. 93,94 More accurate description of optical properties requires GW approximation and the Bethe-Salpeter equation (BSE), 95,96 which are very time-consuming and usually beyond the scope of HT computational design.…”