Impact of Lateral Effects on EQE Measurements of Large Scale Tandem Solar Cells

Laterally inhomogeneous cell parameters in large scale perovskite/silicon (PSC/Si) tandem solar cells may significantly influence the device performance. The lateral quality of the absorber can be analysed with electroluminescence (EL), photoluminescence (PL) and thermographic methods. In addition to a global impact on cell performance, such lateral effects are often not considered in EQE and I-V-characterization of tandem devices, yet may lead to erroneous measurement results. Therefore, we see the necessity to employ large-area 3D PSC/Si-tandem simulations to understand the impact of lateral inhomogeneities, and the interaction with non-ideal measurement conditions such as small-area or non-uniform illumination of the solar cell. We use a tandem addon of the 3D simulation software Quokka3 for our full-cell 3D tandem simulations which treats the perovskite top cell skin, and optionally also the Si bottom cell, with an “equivalent-circuit” model instead of solving the drift-diffusion model. We present simulations and experiments to quantify the impact of inhomogeneous cell properties such as low localized shunt resistances or non-uniformities of the cell absorber, in interaction with the illumination and biasing conditions during the EQE measurement. It is specifically interesting to gain insight into lateral effects by simulation, as the experimental investigation of such detailed effects in often metastable PSC/Si tandem cells is highly challenging.