Tunable Semiconductors: Control over Carrier States and Excitations in Layered Hybrid Organic-Inorganic Perovskites

Abstract

For a class of 2D hybrid organic-inorganic perovskite semiconductors based on π-conjugated organic cations, we predict quantitatively how varying the organic and inorganic component allows control over the nature, energy and localization of carrier states in a quantum-well-like fashion. Our first-principles predictions, based on large-scale hybrid density-functional theory with spin-orbit coupling, show that the interface between the organic and inorganic parts within a single hybrid can be modulated systematically, enabling us to select between different type-I and type-II energy level alignments. Energy levels, recombination properties and transport behavior of electrons and holes thus become tunable by choosing specific organic functionalizations and juxtaposing them with suitable inorganic components.Hybrid organic-inorganic perovskites (HOIPs), [1, 2] particularly three-dimensional (3D) HOIPs, are currently experiencing a strong revival in interest as economically processable, optically active semiconductor materials with excellent transport characteristics. Their success is showcased most prominently by record performance gains in proof-of-concept photovoltaic [3][4][5][6][7][8][9][10][11][12] and light-emitting devices. [13][14][15][16][17][18][19][20] The electronic function of 3D HOIPs can be tuned to a limited extent by manipulating the inorganic component (from which the frontier orbitals are derived), but the organic cations are confined by the 3D structure and are thus necessarily small (e.g., methylammonium [3][4][5][6][7][8][13][14][15][16][17][18] and formamidinium [9-11, 19, 21, 22]), with electronic levels that do not contribute directly to the electronic functionality. [23][24][25][26][27][28] However, the accessible chemical space of HOIPs extends well beyond the 3D systems. [1] In particular, the layered, socalled two-dimensional (2D) perovskites do not place a strict length constraint on the organic cation. In these materials, a much broader range of functional organic molecules can be incorporated within the inorganic scaffolds, including complex functional molecules such as oligo-acene or -thiophene derivatives. [1,[29][30][31][32][33][34][35][36][37] Fig. 1a shows the atomic structure of a paradigmatic example of such a 2D HOIP with active organic functionality, bis(aminoethyl)-quaterthiophene lead bromide AE4TPbBr 4 .[34] Similar juxtapositions of targeted organic and inorganic components give rise to a vast, yet systematically accessible space of possible semiconductor materials, [1, 2,[38][39][40] including those in which the molecular carrier levels contribute directly to the low-lying excitations and carrier levels. [1, 30-32, 34, 38, 39, 41] This large space of conceivable organic-inorganic combinations thus offers the unique opportunity to tailor (ideally with computational guidance) materials with particularly desirable semiconductor properties, by intentionally controlling the spatial location and character of the electronic carriers and optical excitations throughout the m...

Structural and Electronic Impact of an Asymmetric Organic Ligand in Diammonium Lead Iodide Perovskites

“…[ 17 ] However, the choice of diammonium ligand appears to have a more drastic effect on the electronic properties. [ 18,19 ] The optical absorption spectra of several n = 1 films with similar inorganic composition and different ligands ( Figure 1 a) indeed show a significant variation in the optical gap. While using a shorter ligand like ethane‐1,2‐diammonium actually yields a lower 0D perovskite structure, [ 20 ] the layered phase remains intact with the other ligands, yet the bandgap varies significantly.…”

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

“…214,271 This has recently been confirmed using GKS DFT calculations including SOC, revealing a type II band alignement. 272 A c c e p t e d M a n u s c r i p t…”

Memristors with organic‐inorganic halide perovskites

“…Over the past few years, OHPs have been studied extensively for use in photovoltaics because of their remarkable optical and electronic properties . The rapid increase of photovoltaic efficiency has been accompanied by a deeper understanding of the physical/chemical properties of OHPs . Recently, there has been interests in applying OHPs to other photonic and electronic devices, including light‐emitting diodes, X‐ray detectors, and energy conversion devices .…”

“…7,8 The rapid increase of photovoltaic efficiency has been accompanied by a deeper understanding of the physical/chemical properties of OHPs. [46][47][48][49] Recently, there has been interests in applying OHPs to other photonic and electronic devices, including light-emitting diodes, X-ray detectors, and energy conversion devices. [50][51][52][53] It is expected that OHPs will become important active materials for nextgeneration devices in the near future.…”