Scalable all-perovskite double- and triple-junction solar modules: Modeling for configuration optimization

We modeled the photovoltaic conversion of all-perovskite (PVK) double- and triple-junction solar modules to clarify the configurations suitable for the monolithically series-interconnected structure, which offers high scalability by fully exploiting the advantages of the thin-film modules over wafer-based crystalline-silicon modules. We first formulated the photovoltaic processes of single cells and modules by reference to previously reported data, next optimized the module structure parameters including the bandgaps of PVKs, cell widths, and transparent-electrode thicknesses, and then evaluated the annually averaged conversion efficiencies (eta(annual)) defined by the ratio of the annual energy yield to the annual insolation in outdoor environments using a meteorological database. The double-junction four-terminal (2J-4T) module overcomes the shortcomings involved in the two-terminal module consisting of series-connected top and bottom cells, providing higher eta(annual) and more options of the top-cell bandgap; the latter allows us to select a more durable PVK composition. However, the dual output (four terminals) is practically a serious drawback. The double-junction voltage-matched (2J-VM) configuration eliminates this drawback, that is, realizes the single output (two terminals) with taking over the advantages of 2J-4T, and hence, 2J-VM would be the most promising candidate. However, when the VM configuration is applied to the triple-junction modules, the ohmic loss and optical loss in the transparent electrodes used for the three submodules are more detrimental. To mitigate this shortcoming, we proposed a new configuration of the triple-junction series/parallel-connecting voltage-matched (3J-SPVM) module. This uses only two substrates with securing high eta annual and other advantages of the VM configuration, which contributes to cost reduction. Consequently, 3J-SPVM is potentially the most promising configuration for widespread use.