Voltage-matched all-perovskite multijunction bifacial solar modules for albedo utilization and vertical photovoltaics: Modeling and energy-yield analyses

Voltage-matched (VM) configurations for multijunction solar modules consist of the parallel connection of submodules whose maximum-power voltages (VMP) are approximately the same. The VM architectures are intrinsically tolerant to solar-spectrum variation and resulting imbalance in the absorbed solar photons among the submodules because VMP is insensitive to the absorbed photon flux, and hence, well suited to various applications. Exploiting this versatility, we propose bifacial multijunction solar modules composed of organic–inorganic perovskites in the present study. Monolithically series-interconnected structures are adopted because they are compatible with the voltage matching; VMP is tuned by adjusting the stripe-shaped subcell widths, as well as being suitable for mass production. We design double-junction modules using wide-bandgap (WBG) and narrow-bandgap (NBG) submodules with transparent electrodes on the rear faces for surface-albedo utilization. Furthermore, we design a symmetric triple-junction module for vertical installation, in which an NBG submodule is sandwiched between two WBG submodules. Model calculations revealed that these bifacial modules achieve high conversion efficiencies competitive with those of conventional four- and six-terminal modules in which the submodules operate independently. For east-west-facing vertical modules, high efficiencies are maintained throughout the daytime even when the solar intensities onto the front and rear faces are extremely different, as in the early morning and late afternoon. Thus, the proposed bifacial VM modules offer practically attractive architectures for all-perovskite multijunction photovoltaics, because they provide a single electrical output while retaining the high energy yields of multi-terminal designs.