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Based on thin film optics (TFO) and finite element method (FEM), we have theoretically investigated improving external quantum efficiency (EQE) by anti-reflection (AR) films constructed from subwavelength nano multi-layers (NML) of low and high index materials, where the low and high index materials are MgF2 and Ta2O5, respectively. This kind of NML dielectric structures have the advantages of low-cost and flexible. Three kinds of substrates have been studied here, which are glass, polyethylene naphthalate (PEN), and polyethylene terephthalate (PET), respectively. TFO theory has been used to obtain the transmittance and reflectance, which agrees well with FEM results. For NML structure, TFO is more efficient than FEM in terms of calculation time and accuracy. The average AR effects (AAREs) are about 3.69%, 3.46% and 3.07% on glass substrate, about 6.15%, 5.56% and 5.02% on PEN substrate, and about 5.06%, 4.62% and 4.17% on PET substrate, for AR bands (ARBs) 350~800 nm, 350~1100 nm and 350~1500 nm, respectively. The results also reflect that wider AR bandwidth needs more NML layers. In practice, this kind of AR films can be widely applicable to enhance the EQE of the optoelectronic devices (OEDs).

Perovskite/silicon tandems have the potential to surpass the efficiencies possible with single-junction silicon solar cells. Recently, perovskites with wide bandgaps have been demonstrated that can reduce the thermalization losses and make it feasible to boost the efficiency. However, perovskite/silicon tandems on planar silicon cells are multi-layered devices that exhibit strong interference which makes current matching difficult to achieve in two-terminal devices. We perform comprehensive optical modeling of perovskite/silicon tandems with a range of different bandgap perovskites and textures to determine the top-cell thicknesses necessary to achieve current matching for varying top-cell bandgap. Our results show it is possible to achieve 27% efficiency with 1.67 eV bandgap perovskite, and even higher efficiency is possible by minimizing parasitic losses.

In this work solar cell anti-reflection coatings tuned to give a specific hue under solar illumination are investigated. We demonstrate that it is possible to form patterned coatings with large color contrast and high transmittance. We use colorimetric and thin film optics models to explore the relationship between the color and performance of bilayer anti-reflection coatings on crystalline Si, amorphous Si and GaAs. The colorimetric predictions were verified by measuring a series of coatings deposited on Si substrates. Finally, a patterned Si sample was produced using a simple, low-cost photolithography procedure to selectively etch only the top layer of a bilayer coating to demonstrate a high-performance anti-reflection coating with strong color contrast.

We present a new method for measuring thicknesses and refractive indices of ultrathin, thin and relatively thick films by using multi-parametric surface plasmon resonance (MP-SPR). The layers measured can be multiple layers of organic, inorganic, metallic, and it is also possible to follow interaction kinetics of interaction components with all these materials. In this paper, MP-SPR is applied as a method for optimization of thin film deposition, here vacuum evaporation.

The properties of thin-film silicon strongly depend on the deposition method, conditions and the substrate material. The analysis of the microstructure of thin silicon films requires diagnostic tools which are independent on substrate or device concept. In this contribution Raman spectroscopy as a powerful tool for analyzing the microstructure and material phase of hydrogenated amorphous silicon (a-Si:H) and microcrystalline silicon (μSi:H) is discussed. To improve the sensitivity for the bulk properties, a HeNe laser (λ = 633 nm) source is used, due to its longer absorption path length at this wavelength. Partial transmission of the light through the film onto the substrate results in a measured Raman spectrum consisting of the superposition of the spectra of film and substrate. Two methods using different approaches in thin film optics for distinguishing the substrate- and film spectrum from the measurement are discussed. One method to model transmission of the Raman spectrum originating from the substrate is based on thin film interference, adapted to a partial coherent quasi monochromatic light source.[1] This method is applicable in the limiting case of thin a-Si:H films (film thickness: d

Thin film coatings use optical interference to achieve performance. Improved processes and design techniques are yielding advances in design, stability, and performance, particularly in short pulse applications like telecommunications but there are still unsolved problems.