Room-Temperature Optical Tunability and Inhomogeneous Broadening in 2D-Layered Organic–Inorganic Perovskite Pseudobinary Alloys

Abstract

We focus here our attention on a particular family of 2D-layered and 3D hybrid perovskite molecular crystals, the mixed perovskites (C6H5-C2H4-NH3)2PbZ4(1-x)Y4x and (CH3-NH3)PbZ3(1-x)Y3x, where Z and Y are halogen ions such as I, Br, and Cl. Studying experimentally the disorder-induced effects on the optical properties of the 2D mixed layered materials, we demonstrate that they can be considered as pseudobinary alloys, exactly like Ga1-xAlxAs, Cd1-xHgxTe inorganic semiconductors, or previously reported 3D mixed hybrid perovskite compounds. 2D-layered and 3D hybrid perovskites afford similar continuous optical tunability at room temperature. Our theoretical analysis allows one to describe the influence of alloying on the excitonic properties of 2D-layered perovskite molecular crystals. This model is further refined by considering different Bohr radii for pure compounds. This study confirms that despite a large binding energy of several 100 meV, the 2D excitons present a Wannier character rather than a Frenkel character. The small inhomogeneous broadening previously reported in 3D hybrid compounds at low temperature is similarly consistent with the Wannier character of free excitons.

Quantum and Dielectric Confinement Effects in Lower-Dimensional Hybrid Perovskite Semiconductors

“…They also afford an ideal platform to investigate fundamental physical processes in a hybrid 2D system with self-organized vertical growth. [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76] Until very recently, experimental studies on pure multilayered halide perovskites (n>1) were scarce as a consequence of growth and purity issues and were basically limited to bilayered systems (n = 2). 28,31,29,52,32,61,77,18,78,19,[79][80][81][82][83][84][85][86][87][88] Thanks to new synthetic routes, 80 phasepure higher n-members have recently been obtained leading to breakthroughs reported in Nature 20 and Science.…”

Solid-State Physics Perspective on Hybrid Perovskite Semiconductors

“…It allows a consistent theoretical analysis of the influence of halogen alloying on the excitonic properties of layered HOP exactly like in Ga 1-x Al x As, Cd 1-x Hg x Te conventional semiconductor pseudobinary alloys. 79 Figure 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 Until recently, empirical modeling of dielectric confinement in layered HOP relied on crude models with ad-hoc abrupt interfaces. Recently, we have introduced the basic concepts needed to model dielectric confinement beyond an abrupt interface, based on the atomic structure of the interface.…”

Exciton dynamics and non-linearities in two-dimensional hybrid organic perovskites

“…Indeed, both ∆Γ X and − ∆f X f X are proportional to the exciton density and to the square of the exciton Bohr radius [49,50]. In GaAs QWs, the exciton Bohr radius is ∼6.4 nm whereas it is ∼0.75nm in PEPI, leading to a factor ∼ 73 between the square of both Bohr radii [52]. Therefore, by normalizing the carriers densities by the square of exciton Bohr radii, it is possible to say that the experimental conditions are relatively close, supporting the idea that these experiments are performed in the low density regime.…”