The extraordinary progresses in the design and realization of structures in inorganic or organic thin films, whether or not including nanoparticles, make it possible to develop devices with very specific properties. Mastering the links between the macroscopic optical properties and the optogeometrical parameters of these heterogeneous layers is thus a crucial issue. We propose to present the tools used to characterize and to model thin film layers, from an optical point of view, highlighting the interest of coupling both experimental and simulation studies for improving our knowledge on the optical response of the structure. Different examples of studies are presented on copper indium gallium selenide, perovskite, P3HT:ZnO, PC70BM, organic layer containing metallic nanoparticles, and colored solar cells.
The extraordinary progresses in the design and realization of structures in inorganic or organic thin films, whether or not including nanoparticles, make it possible to develop devices with very specific properties. Mastering the links between the macroscopic optical properties and the opto-geometrical parameters of these heterogeneous layers is thus a crucial issue. We propose to present the tools used to characterize and to model thin film layers, from an optical point of view, highlighting the interest of coupling both experimental and simulation studies for improving our knowledge on the optical response of the structure. Different examples of studies are presented on CIGS, Perovskite, P3HT:ZnO, PC70BM, organic layer containing metallic nanoparticles and colored solar cells.
We propose a method under the effective mass approximation with an original formulation that applies to quantum wells, circular quantum wires, and spherical quantum dots of arbitrary materials with sizes as small as 1 nm. Hundreds of structures are resolved on the second scale on a laptop, allowing for optimization procedures. We demonstrate its capability by confronting bandgap calculations with exhaustive literature data for CdS, CdSe, PbS, and PbSe nanoparticles. Our approach includes a correction of the mass to address the nonparabolicity of the band structure. The correction gives an accuracy comparable to more demanding calculation methods, such as eight-band k·p, tight-binding, or even semiempirical pseudopotential methods. The effect of the correction is shown on the intrasubband optical properties of InGaAs/AlGaAs coupled quantum wells.
We present an improved and efficient numerical method to determine the optical properties of nanostructures starting from the electronic properties. We study the variation of electronic and optical properties induced by confinement effects in semiconductors quantum objects. We solve the time-independent Schrödinger equation with a new formulation of a shooting method under the effective mass approximation. This formulation is adapted to quantum wells, circular cross-section quantum wires and spherical quantum dots. We applied a correction on the mass to take into account the nonparabolicity of the band structure. The correction gives an accuracy comparable to more demanding calculation methods such as 8-bands k•p, tight binding or even semi-empirical pseudopotential methods. Our results remain valid even for low-bandgap materials and sizes as small as 1 nm. The calculation speed of our method allows optimization procedures that give better understanding of experimental results concerning CdS, CdSe, PbS and PbSe spherical quantum dots. We consider extensive data from the literature. We focus on the relations between the electronic structure and absorption and photoluminescence spectra measured on spin-coated PMMA thin-films containing (core)shell nanoparticles.
We propose a SnOx | Ag | SnOx multilayer, deposited in a continuous vacuum atmosphere by E-beam evaporation, as transparent anode for a (poly-3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk heterojunction based Organic Solar Cell (OSC). Optical characterization of the deposited SnOx is performed to determine the dispersion of the complex refractive index. A Transfer Matrix Method (TMM) numerical optimization of the thicknesses of each layer of the electrode is realized to limit the number of manufactured samples. A numerical study using the morphology of the silver inserted between the oxide layers as input data is performed with a Finite Difference Time Domain (FDTD) method to improve the accordance between measurement and optical model. Multilayers are manufactured with the objective to give to the electrode its best conductivity and transparency in the visible spectral range by using the results of the optical optimization. These bare tri-layer electrodes show low sheet resistance (<10 Ω/□) and mean transparency on [400-700] nm spectral band as high as 67 % for the whole Glass | SnOx | Ag | SnOx structure. The trilayer is then numerically studied inside a P3HT:PCBM bulk heterojunction based OSC structure. Intrinsic absorption inside the sole active layer is calculated giving the possibility to perform optical optimization on the intrinsic absorption efficiency inside the active area by considering the media embedding the electrodes.
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