Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation

Abstract

This study presents a combined experimental and theoretical study of the electronic structure of two two-dimensional (2D) metal halide perovskite films. Ultraviolet and inverse

Exploiting Two‐Step Processed Mixed 2D/3D Perovskites for Bright Green Light Emitting Diodes

“…With the increase of BABr:PbBr 2 ratio, the mixed BABr/PbBr 2 film gets closer to the 2D BA 2 PbBr 4 film. Especially, for the film made with BABr:PbBr 2 = 1:2, a diffraction peak at 6.4° is visible which is similar to the value reported for BA 2 PbBr 4 . After spin‐coating FABr solution and then thermal annealing, the PbBr 2 and mixed BABr/PbBr 2 films are converted to the FAPbBr 3 or mixed 2D/3D perovskite films (Figure d).…”

“…Especially, for the film made with BABr:PbBr 2 = 1:2, a diffraction peak at 6.4° is visible which is similar to the value reported for BA 2 PbBr 4 . [40] After spin-coating FABr solution and then thermal annealing, the PbBr 2 and mixed BABr/PbBr 2 films are converted to the FAPbBr 3 or mixed 2D/3D perovskite films ( Figure 1d). For all these films, the dominant diffraction peak is located around 14.7°, which can be attributed to 3D FAPbBr 3 .…”

Quantum Well Energetics of an n = 2 Ruddlesden–Popper Phase Perovskite

“…Using the Tauc method, [20] the optical gap is determined to be 2.21 eV, smaller than the 2.38 eV found for the n = 1 analogous iodide RPP, BA 2 PbI 4 . [14] X-ray diffraction (XRD) shows the existence of (020) and (040) peaks characteristic of horizontal stacking as well as the (111) and (202) peaks characteristic of vertical stacking suggesting a mixed orientation of grains ( Figure 1b). The interlayer spacing is 1.978 nm, which is structurally consistent with the 1.383 nm spacing in the BA 2 PbI 4 given the additional Pb-I layer in each repeating unit.…”

“…The interlayer spacing is 1.978 nm, which is structurally consistent with the 1.383 nm spacing in the BA 2 PbI 4 given the additional Pb-I layer in each repeating unit. [10,14]…”

“…[12] The organic ligand, in addition to determining the barrier thickness, controls the height of the energetic barrier of the quantum wells, and out-ofplane mobility. [13] In order to harness the tunability and design appropriate RPPs for each application, a deeper understanding of how tuning these quantum wells affects their energetics is needed.The direct experimental determination of ionization energy [10] (IE) and electron affinity (EA) [14] has been reported for two 2D n = 1 RPPs, but not for higher order (n > 1) materials. These RPPs present a challenge in the fabrication of phase pure films for surface sensitive measurements, as the materials often comprise phases with different n's.…”