Optical constants of CH_3NH_3PbBr_3 perovskite thin films measured by spectroscopic ellipsometry

Abstract

The lack of optical constants information for hybrid perovskite of CH₃NH₃PbBr₃ in thin films form can delay the progress of efficient LED or laser demonstration. Here, we report on the optical constants (complex refractive index and dielectric function) of CH₃NH₃PbBr₃ perovskite thin films using spectroscopic ellipsometry. Due to the existence of voids, the refractive index of the thin films is around 8% less than the single crystals counterpart. The energy bandgap is around 2.309 eV as obtained from photoluminescence and spectrophotometry spectra, and calculated from the SE analysis. The precise measurement of optical constants will be useful in designing optical devices using CH₃NH₃PbBr₃ thin films.

Revealing the Chemistry between Band Gap and Binding Energy for Lead‐/Tin‐Based Trihalide Perovskite Solar Cell Semiconductors

“…For example, Quarti et al reported experimental E g valueso f1.65, 1.61, and 1.69 eV for the orthorhombic (4 K), tetragonal (160 K), and pseudocubic (330 K) phases of CH 3 NH 3 PbI 3 . [127] These data show am arginal variation in E g valuesb etween the three phases (all within 0.17 eV), which is unsurprising, according to Leguy et al [128,129] In agreement with the view of Leguy et al, [128] we further noted that there has been aw ide variation in the experimentally determined band gaps reported for CH 3 NH 3 PbBr 3 .T his variation originated from different research groupsw ith different experimental settings to give E g values of 2.33, [86] 2.309, [131] 2.24, [128] and 2.12 eV. [132] Similarly, E g values of 2.97, [128] 3.06, [86] and 3.11eV [91,130] werer eportedf or CH 3 NH 3 PbCl 3 ,a nd so on.…”

“…In agreement with the view of Leguy et al., we further noted that there has been a wide variation in the experimentally determined band gaps reported for CH 3 NH 3 PbBr 3 . This variation originated from different research groups with different experimental settings to give E g values of 2.33, 2.309, 2.24, and 2.12 eV . Similarly, E g values of 2.97, 3.06, and 3.11 eV were reported for CH 3 NH 3 PbCl 3 , and so on.…”

Temperature-dependent optical spectra of single-crystal (CH3NH3)PbBr3 cleaved in ultrahigh vacuum

“…Temperature-dependent measurements can help to develop a more complete picture of these optical properties, which needs to include identification of exciton binding energies, free carriers, as well as direct and possible indirect transitions. Direct measurements of optical absorption spectra of single crystals in transmission are hindered by the short absorption length of visible light in OIPS [52], which forms a basis of their successful application in optoelectronics. Measurements in reflectance are surface-sensitive, and easily affected by hydration of the surface [35,45].…”

Surface Plasmon Enhanced Strong Exciton–Photon Coupling in Hybrid Inorganic–Organic Perovskite Nanowires

“…obtain the E-k dispersion relation of exciton-polariton for NWs on SiO2/Ag substrates, the background dielectric constant b  and damping constant  need to be determined (SI Note 1). The background dielectric constant is calculated from the spectroscopic ellipsometer [51][52][53]. With the dielectric function ε(E) = ε1(E) + iε2(E) and the refractive index N(E) = n(E) + ik(E) ranging over a wide photon-energy, the n and k could be obtained from the spectroscopic ellipsometer and finally the background dielectric constant b  can be calculated as ε1 = n 2 -k 2 and b  is dielectric constant located at    .…”