Voltage-Matched All-Perovskite Double- and Triple-Junction Solar Modules for Building-Integrated Photovoltaics

We designed multijunction solar modules for installation on building walls, in which all the submodules are composed of organic–inorganic hybrid perovskite solar cells, adopting the monolithically series-interconnected structures. Prior to considering concrete module configurations, we elucidated that the impacts of temporal and regional variations in the solar spectra on the vertically wall-installed modules are more notable than those on the modules installed on rooftops and in solar farms at the optimal tilt angles. As a result, the annually averaged conversion efficiencies for the double-junction (2J) modules of the conventional two-terminal configuration and other configurations that require the current matching between the top and bottom modules are notably degraded. By contrast, the voltage-matched (VM) 2J modules, in which the submodules yielding approximately the same maximal-power voltages (V_MP) are connected in parallel, ensure high conversion efficiencies close to those for the four-terminal (4T) 2J modules even when wall installed because V_MP is less sensitive to solar-spectrum variation than the photocurrents. The single output of the VM 2J modules is practically a great advantage over the dual output of the 4T 2J modules. An improved variant: the series–parallel-connecting VM triple-junction modules, in which the two-terminal middle/bottom modules are parallel connected with the top modules, further improve the conversion efficiencies under all the installation conditions.