Realistic absorption coefficient of each individual film in a multilayer architecture

Abstract

A spectrophotometric strategy, termed multilayer-method (ML-method), is presented and discussed to realistically calculate the absorption coefficient of each individual layer embedded in multilayer architectures without reverse engineering, numerical refinements and assumptions about the layer homogeneity and thickness. The strategy extends in a non-straightforward way a consolidated route, already published by the authors and here termed basic-method, able to accurately characterize an absorbing film covering transparent substrates. The ML-method inherently accounts for non-measurable contribution of the interfaces (including multiple reflections), describes the specific film structure as determined by the multilayer architecture and used deposition approach and parameters, exploits simple mathematics, and has wide range of applicability (high-to-weak absorption regions, thick-to-ultrathin films). Reliability tests are performed on films and multilayers based on a well-known material (indium tin oxide) by deliberately changing the film structural quality through doping, thickness-tuning and underlying supporting-film. Results are found consistent with information obtained by standard (optical and structural) analysis, the basic-method and band gap values reported in the literature. The discussed example-applications demonstrate the ability of the ML-method to overcome the drawbacks commonly limiting an accurate description of multilayer architectures.

Pulsed photoinitiated fabrication of inkjet printed titanium dioxide/reduced graphene oxide nanocomposite thin films

“…The complex morphology of the nanostructured films presents a challenge for successfully modeling and determining the absorption coefficient of the material. By using the multilayer-method, film inhomogeneity, surface roughness caused scattering, and the sample's layered architecture were accounted for [81,82]. The multilayer-method requires transmission and reflection data of both the uncoated and coated substrates.…”

“…The multilayer-method requires transmission and reflection data of both the uncoated and coated substrates. The absorption coefficient for the TiO 2 layer is calculated according to the formulas described by Cesaria et al [81,82] It is important to note that the substrate consists of 150 nm ITO coated on a 1.1 mm thick glass slide and an additional 1.1 mm thick glass slide for sample mounting. The inhomogeneity of the TiO 2 layer is accounted for in the model, as the thickness term of the TiO 2 layer describes the relative thickness of the TiO 2 versus the substrate.…”

Charge carrier dynamics and interfaces in perovskite solar cells

“…Furthermore, beams reflected at the bottom or at the film-substrate interface are not neglected in the calculation. Therefore, this calculation is deemed realistic because it does not disregard the influences of the scattering from the internal interfaces and the film-volume interface [143].…”