Investigating the Tradeoff Between Transparency and Efficiency in Semitransparent Bifacial Mesosuperstructured Solar Cells for Millimeter-Scale Applications

This article thanks to recent advancements in nanofabrication and 3-D packaging, typical Internet of Things devices can now be wirelessly controlled using millimeter-scale sensors known as Internet of Tiny Things devices. Since these low-power devices may be exposed to low and indirect solar irradiation, we demonstrate a novel mesosuperstructured solar cell (MSSC) that allows low flux light to be harvested from both its top and bottom sides. Our cell is based on either a dye-sensitized solar cell (DSSC) or a perovskite solar cell (PSC). The active layer in the proposed MSSCs was tuned to allow semitransparent behavior. Moreover, we developed an experimentally validated model that enables optimization of the active layer thickness for different semitransparent MSSC applications. In MSSCs, such optimization is necessary to balance the tradeoff between transparency and efficiency for various active layer thicknesses. Fabricated DSSCs and PSCs cells were used to validate the simulation results. The fabricated DSSC achieved a harvesting ratio of 1:10 with a conversion efficiency of around 2% at one Sun. We demonstrate that the optimum thickness of the mesoporous TiO
₂
active layer in DSSCs was 800 nm, enabling a maximum power density of 7 mW/cm
²
.