Understanding Quantum Confinement of Charge Carriers in Layered 2D Hybrid Perovskites

Abstract

Keywords: 2D materials, density functional calculations, hybrid perovskites, quantum confinement, semiempirical calculations Layered Hybrid Organic Perovskites (HOP) structures are a class of low-cost twodimensional (2D) materials that exhibit outstanding optical properties, related to dielectric and quantum confinement effects. While modeling and understanding of quantum confinement are well developed for conventional semiconductors, such knowledge has still to be gained for 2D HOP. In this work, concepts of effective mass and quantum well are carefully investigated and their applicability to 2D HOP is discussed. For ultrathin layers, the effective mass model fails. Absence of superlattice coupling and importance of non-parabolicity effects prevents the use of simple empirical models based on effective masses and envelope function approximations. We suggest an alternative approach where 2D HOP are treated as composite materials and introduce a first principles approach to band offsets calculations. These findings may also be relevant for other classes of layered 2D functional materials.

Perovskite Materials for Light‐Emitting Diodes and Lasers

“…[87] Formation of 1.2 nm-thick CH 3 NH 3 PbBr 3 NPLs was demonstrated via non-templated routes and, [57] although PL emission could not be observed due to the low concentration of NPLs, the absorption peak at 431 nm was blue-shifted ≈0.5 eV compared to that in the bulk. [56,88] Additional absorption maxima at 431, 451, 472, and 525 nm, corresponding to n = 1, 3, 4, and ∞, respectively, were in agreement with earlier reports for layered perovskites. [56,59] Similarly, changes in the size, morphology, and PL emission were observed by adjusting the ratio between methylammonium and octylammonium cations [16,73] The blue-shifts originating from quantum confinement are partially counteracted due to the high binding energy (several hundred meV) found for NPLs of n < 3.…”

Excitons in ultrathin organic-inorganic perovskite crystals

“…In the OIPCs the smaller dielectric constant of the organic layers leads to decreased screening between the electron and the hole and, thus, to an additional increase of the exciton binding energy beyond the prediction for an idealized 2D system. 19,20,24,32,46 To probe the excitonic properties of the NSs, we measured the excitonic Rydberg series, that is, the excited states of the exciton. The allowed single-photon transitions typically involve excitonic states with zero angular momentum, which we label in analogy to the hydrogenic series by the principal quantum number as 2s, 3s, etc.…”

Les pérovskites hybrides : des excitons sur mesure pour l’optoélectronique

“…Pour m = 1, le puits est constitué d'une couche d'octaèdres, large d'une fraction de nanomètre (figure 2). À ce grand confinement quantique, il faut ajouter des effets de confinement dié-lectrique dus à une grande différence de constante diélectrique entre les feuillets organiques et inorganiques, qui localisent strictement la fonction d'onde des électrons et des trous dans la couche inorganique [7]. Ainsi, le confinement des porteurs est quasi purement bidimensionnel dans la En conclusion, la famille des pé-rovskites hybrides est vaste et est abonnée aux records : 5 ans seulement après la découverte de leur potentiel pour le photovoltaïque, des premières étapes importantes ont été franchies vers la commercialisation de cellules solaires les contenant, comme le prouvent les investissements récents de l'entreprise OxfordPV.…”