Design and characterization of nanometric resonant structures and advanced concentration strategies applied to photonic devices

  1. Hamdy Mohamed Elshorbagy, Mahmoud
Dirigida por:
  1. Alexander Cuadrado Conde Director
  2. Javier Alda Director

Universidad de defensa: Universidad Complutense de Madrid

Fecha de defensa: 23 de septiembre de 2020

Tribunal:
  1. Luis Miguel Sánchez-Brea Presidente
  2. José Manuel López Alonso Secretario
  3. Rosalía Serna Galán Vocal
  4. Fernando Moreno Gracia Vocal
  5. Miguel Manso Silván Vocal
Departamento:
  1. Óptica

Tipo: Tesis

Resumen

Efficient low-cost optoelectronic devices are used for many applications, for example, energy production, and sensing. The development of these devices can be step-forward using nanophotonic and nanoplasmonic structures. In this dissertation we propose, design, and analyze several nanostructures to improve the performance of these devices. For energy applications, we select amorphous silicon hydrogenated, and perovskite/crystalline silicon tandem solar cells. We choose amorphous silicon solar cells because this material is abundant, non-toxic, long-life compared to organic solar cells, and can be fabricated at a low cost. The tandem perovskite/crystalline silicon solar cells are devices with potential power conversion efficiency more 30 percent. Our designs are based on dielectric nanostructures. We applied a 1D nanostructure array to the top and bottom of amorphous silicon hydrogenated solar cells, in two separate designs. The absorption enhancement within the auxiliary layers of these devices is dissipated as heat and partially mitigate the defects resulted from the Staebler Wronski effect. A metasurface in the form of multilayer gratings embedded in the active layer of the perovskite top cell of the tandem device, improves the absorption efficiency in the whole device. A sawtooth periodic back texture has been optimized and tested to work with the metasurface for further improvement of the device performance. These nanostructures are arranged to maximize the absorption efficiency of the selected solar cells, mainly by reducing their total reflectance. The analysis and calculations are completed by modeling the conditions of the sun illumination, i.e, unpolarized light, and oblique incidence. The performance of the devices is calculated under these conditions. We used metallic gratings with different arrangements embedded in a dielectric buffer layer to excite surface plasmon resonances at metal/dielectric interfaces using normal incidence conditions. We optimize the designs using a merit function, which is carefully selected to maximize the sensing characteristics: sensitivity, figure of merit, and dynamic range. Two different optimized metallic gratings (nanoslits, and multilayer metal/dielectric grating structure) provide sensors with high sensitivity and figure of merit. However, the dynamic range of these devices is limited. High refractive index scatterers made of dielectric material embedded in low refractive index host, improve the dynamic range of the proposed devices. The improvement is attributed to the high refractive index contrast around the scatterers. We optimize several designs to work as refractometric sensors: ZnO nanoprisms embedded in MgF2 substrate, a Si3N4 high aspect ratio grating in the analyte, and a GaP rectangular grating embedded in a MgF2 buffer layer. We found that a GaP rectangular grating in a MgF2 buffer layer produces a Fano resonance, and provides a sensor for which the three characteristics of the senor are enhanced together. In this case, the refractive index contrast of the scatterer is the largest one obtained with the studied materials. A high sensitivity, and figure of merit over a wide range of changes in the refractive index of the sensed medium were achieved. We also proposed hybrid devices that can produce an electrical signal, and enhance their capabilities for sensing applications. We do that by exciting plasmonic resonances in these devices, and make them spectral selective. The direct readout of the electrical signal from these devices, and its relation to environmental changes, provides simple operation, low-cost, and compact sensors. A modified figure of merit is adapted for each one of these direct readout devices. We adapt it from the operational mechanism and the working principle of each device.