Energy Yield Analysis of Multiterminal Si-Based Tandem Solar Cells

We present a model for a yield analysis of tandem devices consisting of Si bottom cells with III-V top cells. It accounts for the spectral properties of the subcells as well as their reduced operating temperature due to increased efficiency and luminescent coupling. Inputs are the experimental I-V and QE data of the subcells (e.g., available from laboratory prototypes) and the irradiance-dependent module temperature of the bottom cell. We apply the model to compare two types of tandem cells, GaInP and GaAs top cells on Si bottom cells. The impact of the temperature model, compared to a constant temperature, shows a relative change in energy yield of up to 2.7%_rel. Including luminescent coupling for GaAs/Si devices with two terminals, increases the energy yield by 34.0%_rel. This is still 34.2%_rel less energy yielded than for GaInP/Si two-terminal devices. The performance of the GaInP/Si devices can be improved by 5.8%_rel using three-terminal devices with back-contacted bottom cells instead of a two-terminal configuration under the assumption of a cell string with voltage matching of one top cell with two bottom cells. For GaInP/Si, the three-terminal device performs similarly to the four-terminal device, enabling the integration of monolithic tandem cells into modules at comparably high efficiencies.