Light Recycling Using Perovskite Solar Cells in a Half‐Cylinder Photonic Plate for an Energy Efficient Broadband Polarized Light Emission

Abstract

Energy efficiency in many illumination devices is far from optimal. For instance, in liquid crystal displays, a large fraction of the emitted light is lost provided absorbing polarizers are used for the image formation. Herein, a light‐guiding structure to achieve diffuse polarized light emission from the top of the guide, combined with light harvesting and conversion back into electricity of the light with the unwanted polarization is proposed. Key in achieving such a double goal is the use of a half‐cylinder photonic plate for an ergodic light‐guided propagation incorporating a nonabsorbing reflective multilayer light polarizer and perovskite (PVK) solar cells. In the complex combination of micro‐ and nanometric dimensions of the proposed structure, light propagation was resolved using ray optics tracing interlaced with a full wave vector inverse integration approach. A broadband polarization extinction ratio of 0.1 for the light diffused from the top surface is demonstrated, while close to 90% of the s‐polarized light remains trapped and can be recycled back to electricity by the PVK solar cells placed on the front and back ends of the guide. PVK cells are shown to be optimal in such conversion with an overall efficiency ranging from 38 to 52%.

Wide Bandgap Perovskite Photovoltaic Cells for Stray Light Recycling in a System Emitting Broadband Polarized Light

“…More specifically, an h‐CPP is employed to achieve ergodic light propagation, which is ideal to obtain a homogeneous light diffusion, and a multilayer reflective polarizer with randomly distributed layer thicknesses is used for broadband light polarization. As demonstrated in our previous study, [ 24 ] the randomness in the multilayer structure is key to achieve a low polarization extinction ratio of ≈0.1 for a broad range spanning the blue, green, and red spectra.…”

“…The polarization extinction ratio as well as the transmitted p-pol light power achieved in the current h-CPP design, could be increased by the use of more uniform deposition methods such as atomic layer deposition or high-power pulsed magnetron sputtering. [36,37] In such scenario, the optimized polarizing structure applied for display illumination could reach a polarized light emission larger than 37% of the total incident light, [24] while the presented WBG perovskite PV cells would recycle the stray light with an average efficiency over 34%. Therefore, the combination of these elements could reduce the power losses relative to devices that incorporate absorbing polarizers by about 20%, as detailed in Section S4 in the Supporting Information.…”

“…A more detailed explanation on the inverse design simulations can be found in ref. [24]. Modified h-CPP Fabrication and Characterization: The h-CPP was fabricated on a transparent polymer (OrmoComp, Micro Resist Technology GmbH) by drop casting it onto a metallic mold patterned with the negative periodic geometry.…”

“…[10][11][12][13][14][15] Moreover, their bandgap energy (E g ) can be widely tuned by engineering the perovskite composition, which promises a high level of adaptability to different specific applications. [16][17][18][19][20][21][22][23] In a previous study, [24] we proposed the design of a novel light guiding plate which would emit polarized light, while the light with the unwanted polarization could be recycled back into electricity by two perovskite PV cells placed at the front and back ends of the guide. A homogeneous diffused light emission was demonstrated as a result of the ergodic light propagation occurring in what was termed as a half-cylinder photonic plate (h-CPP).…”

“…The model provides a powerful combination of ray optics, a transfer matrix formalism, and an optimization algorithm to numerically compute the optimal layer thicknesses by an inverse design approach as described in ref. [24]. In addition, to account for possible experimental thickness deviations, we monitored the thickness of the different layers while the structure was being fabricated and always recalculated the optimal thickness for the following layers to obtain the lowest possible polarization extinction ratios.…”