Toward more reliable measurement procedures of perovskite-silicon tandem solar cells: The role of transient device effects and measurement conditions

Perovskite-silicon (Pero-Si) tandem solar cells have made remarkable progress in recent years, achieving certified cell efficiencies of up to 33.9%. However, accurately measuring the efficiency and current density-voltage (JV) curves of these devices poses various challenges including the presence of mobile ions within the perovskite absorber that lead to short- and long-term transient effects. Consequently, both the measurement setup and the preconditioning of the device significantly affect measurement results. This study focuses on enhancing the reliability and comparability of JV and other efficiency measurements for Pero-Si tandem devices through a systematic analysis of the influence of mobile ions, preconditioning and measurement conditions. For the first time, a full opto-electrical simulation model for Pero-Si tandem devices is presented in Sentaurus TCAD, which includes the drift-diffusion of anions and cations and is therefore able to describe short- and long-term transient device effects in state-of-the-art Pero-Si tandem cells. Experimental validation and evidence are given by comparison to in-house Pero-Si tandem cells, as well as Pero-Si mini modules from Oxford PV. We analyze by simulation and experiment how the cell preconditioning at different preconditioning voltages and times impacts the resulting measured tandem efficiency, as well as impact of JV scan times for the measured hysteresis in Pero-Si tandem devices. Furthermore, we demonstrate the impact of current-mismatching conditions on the measured hysteresis of the Pero-Si tandem device and the need of correct spectral irradiance settings during measurements. We showcase that even a very slight variation in short-circuit current density (j_sc) around the current-matching point leads to significantly different hysteresis behaviors. With aid of our simulation model, we could attribute this phenomenon to a reverse/forward biasing of the perovskite sub-cell impacting the ion drift depending on the current-limiting sub-cell of the tandem device. Therefore, it is sensible to be aware of the current limiting sub-cell for the comparison of the hysteresis susceptibility of different Pero-Si tandem devices. This study strongly underscores the importance of including the preconditioning and measurement conditions when reporting Pero-Si tandem efficiencies. The findings highlight the urgent need for standardization in the field.