For a class of 2D hybrid organic-inorganic perovskite semiconductors based on pi-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.
FIG.(a) Structure of AE4TPbBr4, fully relaxed by DFT-PBE + TS taking the experimental (x-ray diffraction) structure as the input. (b) Possible energy level schemes (Ia, Ib, IIa, IIb) for the alternating organic-inorganic perovskite structure are shown, with the overall band gap indicated by arrows and dashed lines.