Optical and Electronic Properties

In this chapter we present many details on the optical and electronic properties of 2D metal halide perovskites (MHPs). The 2D MHP structure can be thought of as a quantum well superlattice which includes effects from both quantum and dielectric confinement. The lower bandgaps in the metal halide layers form the quantum wells which tend to dominate the electronic structure, and the organic cations serve as the barriers. The dielectric confinement comes from a mismatch in dielectric constant between the wells and barriers, with the organic cations having lower dielectric constants than the inorganic layers. The confinement of electrons and holes to the same 2D layer creates an enhanced excitonic effect compared to 3D perovskites; thus, excitons play a central role in dictating the 2D MHP optoelectronic properties. The papers presented in this chapter include controlling optical and transport properties through composition and structure, dynamically adjusting properties through exposure to water vapor and light, the effects of accidental defects and deliberate doping, and using density functional theory to calculate electronic band structures.