Diseño y caracterización de estructuras resonantes y estrategias de concentración avanzada aplicadasa dispositivos fotónicos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Óptica, leída el 23-09-2020Efficient 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/crystallinesilicon 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 > 30 %. 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 metasurfacef or 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...Los dispositivos optoelectrónicos eficientes y de bajo coste se utilizan en muchas aplicaciones. Por ejemplo, en la producción de energía y en sensores. La incorporacion de estructuras nanofotónicas y nanoplasmónicas es un paso adelante en el desarrollo de estos dispositivos. En esta tesis doctoral proponemos, diseñamos y analizamos varias nano-estructuras que mejoran el rendimiento de estos dispositivos. En aplicaciones para energía, hemos selecionado células de silicio amorfo hidrogenado, y células tándem de perovskitas y silicio cristalino. Hemos elegido las células solares de silicio cristalino porque es un material abundante, no tóxico, de larga vida comparada con las células orgánicas y fabricadas a bajo coste. Las células tándem perovskita/silicio cristalino son dispositivos con eficiencias de conversión superiores al 30 %. Nuestros diseños están basados en nano-estructuras dieléctricas. Hemos aplicado una nano-estructura periódica 1D a la superficie anterior y posterior de células solares de silicio amorfo hidrogenado en dos diseños separados. El aumento de la absorción en las capas auxiliares de estas células se disipa como calor y mitiga parcialmente los defectos producidos por el efecto Staebler-Wronski. Una metasuperficie hecha con redes apiladas en capas incluidas en las capa activa de la porción superior de una célula tándem mejora la eficiencia de absorción de todo el dispositivo...Fac. de Ciencias FísicasTRUEunpu

Funneling and guiding effects in ultrathin aSi-H solar cells using one-dimensional dielectric subwavelength gratings

Ultrathin amorphous silicon hydrogenated (aSi-H) solar cells grown on a one-dimensional (1-D) dielectric subwavelength gratings improve the short circuit current by a factor of more than 51% when compared with conventional, flat ultrathin aSi-H devices. This improvement is possible due to several mechanisms. In addition the increase in exposed area caused by the nanostructured surface, a reliable computational electromagnetic evaluation of the interaction of the solar spectrum with the cell structure demonstrates that absorption at the active layer is enhanced and also reflectivity is decreased. In addition, the absorbed power at the nonactive layers is larger, helping to increase the temperature and mitigate the Staebler–Wronski effect. The detailed analysis of the power flux inside the structure has also shown that funneling and guiding mechanism are at play, increasing the optical path within the active layer that produces a better performance of the cell

Plasmonic Sensor Based on Dielectric Nanoprisms

A periodic array of extruded nanoprisms is proposed to generate surface plasmon resonances for sensing applications. Nanoprisms guide and funnel light towards the metal-dielectric interface where the dielectric acts as the medium under test. The system works under normal incidence conditions and is spectrally interrogated. The performance is better than the classical Kretschmann configurations, and the values of sensitivity and figure of merit are competitive with other plasmonic sensor technologies. The geometry and the choice of materials have been made taking into account applicable fabrication constraints

High-sensitivity integrated devices based on surface plasmon resonance for sensing applications

A metallic nanostructured array that scatters radiation toward a thin metallic layer generates surface plasmon resonances for normally incident light. The location of the minimum of the spectral reflectivity serves to detect changes in the index of refraction of the medium under analysis. The normal incidence operation eases its integration with optical fibers. The geometry of the arrangement and the material selection are changed to optimize some performance parameters as sensitivity, figure of merit, field enhancement, and spectral width. This optimization takes into account the feasibility of the fabrication. The evaluated results of sensitivity (1020 nm/RIU) and figure of merit (614 RIU−1RIU−1) are competitive with those previously reported

Narrow Absorption in ITO-Free Perovskite Solar Cells for Sensing Applications Analyzed through Electromagnetic Simulation

This work reports on a computational analysis of how a modified perovskite cell can work as a refractometric sensor by generating surface plasmon resonances at its front surface. Metal-dielectric interfaces are necessary to excite plasmonic resonances. However, if the transparent conductor (ITO) is replaced by a uniform metal layer, the optical absorption at the active layer decreases significantly. This absorption enhances again when the front metallic surface is nanostructured, adding a periodic extruded array of high aspect-ratio dielectric pyramids. This relief excites surface plasmon resonances through a grating coupling mechanism with the metal surface. Our design allows a selective absorption in the active layer of the cell with a spectral response narrower than 1 nm. The photo-current generated by the cells becomes the signal of the sensor. The device employs an opto-electronic interrogation method, instead of the well-known spectral acquisition scheme. The sensitivity and figure of merit (FOM) parameters applicable to refractometric sensors were adapted to this new situation. The design has been customized to sense variations in the index of refraction of air between 1.0 and 1.1. The FOM reaches a maximum value of 1005 RIU−1 , which is competitive when considering some other advantages, as the easiness of the acquisition signal procedure and the total cost of the sensing system. All the geometrical and material parameters included in our design were selected considering the applicable fabrication constrains

Opto-Electronic Refractometric Sensor Based on Surface Plasmon Resonances and the Bolometric Effect

The bolometric effect allows us to electrically monitor spectral characteristics of plasmonic sensors; it provides a lower cost and simpler sample characterization compared with angular and spectral signal retrieval techniques. In our device, a monochromatic light source illuminates a spectrally selective plasmonic nanostructure. This arrangement is formed by a dielectric low-order diffraction grating that combines two materials with a high-contrast in the index of refraction. Light interacts with this structure and reaches a thin metallic layer, that is also exposed to the analyte. The narrow absorption generated by surface plasmon resonances hybridized with low-order grating modes, heats the metal layer where plasmons are excited. The temperature change caused by this absorption modifies the resistance of a metallic layer through the bolometric effect. Therefore, a refractometric change in the analyte varies the electric resistivity under resonant excitation. We monitor the change in resistance by an external electric circuit. This optoelectronic feature must be included in the definition of the sensitivity and figure of merit (FOM) parameters. Besides the competitive value of the FOM (around 400 RIU −1 , where RIU means refractive index unit), the proposed system is fully based on opto-electronic measurements. The device is modeled, simulated and analyzed considering fabrication and experimental constrains. The proposed refractometer behaves linearly within a range centered around the index of refraction of aqueous media, n≃1.33 , and can be applied to the sensing for research in bio-physics, biology, and environmental sciences

Efficient light management in a monolithic tandem perovskite /silicon solar cell by using a hybrid metasurface

Solar energy is now dealing with the challenge of overcoming the Shockley&-Queisser limit of single bandgap solar cells. Multilayer solar cells are a promising solution as the so-called third generation of solar cells. The combination of materials with different bandgap energies in multijunction cells enables power conversion efficiencies up to 30% at reasonable costs. However, interfaces between different layers are critical due to optical losses. In this work, we propose a hybrid metasurface in a monolithic perovskite-silicon solar cell. The design takes advantage of light management to optimize the absorption in the perovskite, as well as an efficient light guiding towards the silicon subcell. Furthermore, we have also included the effect of a textured back contact. The optimum proposal provides an enhancement of the matched short-circuit current density of a 20.5% respect to the used planar reference.This research was funded by Ministerio de Economía y Competitividad, grant number TEC2016-77242-C3-1-R Grant (AEI/FEDER, UE funds), and Comunidad de Madrid and FEDER program through the SINFOTON-CM Research (grant number S2013/MIT-2790) and SINFOTON2-CM (granT number S2018/NMT-4326) programs

Ultra-narrow spectral response of a hybrid plasmonic-grating sensor

We configure and analyze a nanostructured device that hybridizes grating modes and surface plasmon resonances. The model uses an effective index of refraction that considers the volume fraction of the involved materials, and the propagation depth of the plasmon through the structure. Our geometry is an extruded low-order diffraction grating made of dielectric nano-triangles. Surface plasmon resonances are excited at a metal/dielectric interface, which is separated from the analyte by a high-index dielectric layer. The optical performance of the refractometric sensor is highly competitive in sensitivity and figure of merit (FOM) because of the the ultra-narrow spectral response (below 0.1 nm). Moreover, it is operative within a wide range of the index of refraction (from 1.3 till 1.56), and also works under normal incidence conditions