Porous titanium dioxide (TiO 2) films are essential components of dye sensitized solar cells (DSSCs) as well as perovskite solar cells (PSCs). Unfortunately, porosity, refractive index, and scattering properties of these films are only roughly known. This induces uncertainties in modelling and understanding of these solar cells. Since the literature provides only descriptions of the optical properties of the porous TiO 2 layers with unclear relevance to these solar cells, we investigate porous TiO 2 films really used in DSSCs and potentially usable in PSCs. The effective refractive index and the film porosity for different nanostructures that were fabricated from solution-based techniques were determined. The found values are 1.7982 ± 0.005 for the effective refractive index of one kind of TiO 2 films and 1.62 ± 0.002 for another one. These values lead to porosities of 53.5% and 65%, respectively. The scattering of the films can be described by a wavelength-independent effective scattering parameter for one film type and by effective scattering particles with a diameter of 46.5 nm for the other film type. The determined porosities are also of relevance for the ionic transport which is functionally crucial in DSSCs and a disturbance in PSCs.

A novel structure for thin-film solar cells is simulated with the purpose of maximizing the absorption of light in the active layer and of reducing the parasitic absorption in other layers. In the proposed structure, the active layer is formed from an amorphous silicon thin film sandwiched between silicon nanowires from above and photonic crystal structures from below. The upper electrical contact consists of an indium tin oxide layer, which serves also as an antireflection coating. A metal backreflector works additionally as the other contact. The simulation was done using a new reliable, efficient and generic optoelectronic approach. The suggested multiscale simulation model integrates the finite-difference time-domain algorithm used in solving Maxwell's equation in three dimensions with a commercial simulation platform based on the finite element method for carrier transport modeling. The absorption profile, the external quantum efficient, and the power conversion efficiency of the suggested solar cell are calculated. A noticeable enhancement is found in all the characteristics of the novel structure with an estimated 32% increase in the total conversion efficiency over a cell without any light trapping mechanisms.

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In this work, we propose a micro-scale modulator architecture with compact size, low insertion loss, high extinction ratio, and low energy/bit while being compatible with the silicon-on-insulator (SOI) platform. This is achieved through the utilization of epsilon-near-zero (ENZ) effect of indium-tin-oxide (ITO) to maximize the attainable change in the effective index of the optical mode. It also exploits the ITO layer in a hybrid plasmonic ring resonator which further intensifies the effect of the changes in both the real and imaginary parts of the effective index. By electrically inducing carriers in the indium tin oxide (ITO), to reach the ENZ state, the resonance condition shifts, and the losses of the hybrid plasmonic ring resonator increases significantly. This mechanism is optimized to maximize the extinction ratio and minimize the insertion loss. The proposed structure is designed to maximize the coupling to and from standard SOI waveguide, used as access ports. In addition, the operational region is reconfigurable by changing the bias voltage.

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We propose a novel, compact plasmonic sensing structure based on a metal–insulator–metal waveguide hybridly-coupled to a rectangular side cavity. The structure has been numerically investigated using the finite-difference time-domain method. Transmission spectra obtained from numerical simulations are used to analyze the sensing characteristics of the structure. The effects of the geometrical parameters on transmission and sensing of the structure are studied. With optimum design, sensitivity can reach as high as 1500 nm per refractive-index unit around the resonance wavelength of 1550 nm with a cavity area of 1 μm2. The proposed structure can potentially be applied in on-chip pressure and gas micro-sensors.

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