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

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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.
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