Unraveling the Exciton Binding Energy and the Dielectric Constant in Single-Crystal Methylammonium Lead Triiodide Perovskite

Abstract

We have accurately determined the exciton binding energy and reduced mass of single crystals of methylammonium lead tri-iodide using magneto-reflectivity at very high magnetic fields. The single crystal has excellent optical properties with a narrow line width of ∼ 3 meV for the excitonic transitions and a 2s transition which is clearly visible even at zero magnetic field. The exciton binding energy of 16 ± 2 meV in the low temperature orthorhombic phase is almost identical to the value found in polycrystalline samples, crucially ruling out any possibility that the exciton binding energy depends on the grain size. In the room temperature tetragonal phase, an upper limit for the exciton binding energy of 12 ± 4 meV is estimated from the evolution of 1s-2s splitting at high magnetic field.

Methodologies toward Efficient and Stable Cesium Lead Halide Perovskite‐Based Solar Cells

“…The mixed‐halide CsPbX 3 films (CsPbI 3 , CsPbI 2 Br, and CsPbBr 3 ) were prepared to compare the dependence of the photophysical properties on the halide cage (octahedra network of PbX 6 , X = I, Br). The transmission spectra did not show any structural phase transitions even at extremely low temperature, in contrast to those of the organic counterparts as previously reported ( Figure 13 a, left) 14, 79, 80. It was suggested that the presence of a molecular dipole determines the overall electronic properties of halide perovskites.…”

Review of Novel Passivation Techniques for Efficient and Stable Perovskite Solar Cells

“…One such example is the possible correlation between dielectric constant and defects for perovskites. Although there are a few works on this including the reports of giant dielectric constant . Work is to be done to separate the effect of ions for more accurate future study of defect studies.…”

Halogen in materials design: Fluoroammonium lead triiodide (FNH3PbI3) perovskite as a newly discovered dynamical bandgap semiconductor in 3D

“…It also promotes the understanding of the nature of the hysteresis loop in the J−V curve, facilitating to gain insight into, among others, the transient capacitive current, trapping and detrapping process, ion migration, and ferroelectric polarization, thus a useful tool for determining the power conversion efficiency of any newly discovered perovskite material . Determinations of exciton binding energies, electron‐hole diffusion lengths, defect tolerance, effective carrier masses, and strength of bandgap, as well as an understanding of nature of the band structure, density of states spectra, and the interplay of hydrogen bonding and other noncovalent interactions cover a major part of this area of research, thereby advancing the development of our fundamental understanding of the device chemistry and physics of halide based perovskite materials …”