Multi-scale Simulation of All-Perovskite Tandem Photovoltaics

All-perovskite tandem solar cells hold the promise of a scalable, low-cost, flexible, and high-efficiency photovoltaic technology. However, scaling up to the dimensions targeted
by commercial applications poses a number of challenges. Most importantly, material quality and uniformity of the solution-processed absorber layers is more difficult to control on large area using deposition techniques beyond spin-coating, such as slot-die
coating or ink-jet printing. Similar uniformity issues apply to the charge transport layers, especially the ultra-thin self-assembled monolayers used for interface passivation and enhancement of contact selectivity. Hence, we expect local fluctuations in active area quality to affect the overall photovoltaic performance on the level of monolithic interconnected thin film modules. Also, the monolithic interconnection of the thin film modules requires special considerations regarding the implementation of bypass diodes to prevent damage to the material in the case of partial shading that forces the affected cell into reverse bias. In fact, reverse-bias breakdown in perovskite solar cells is receiving increased attention due to the peculiar role of the mobile ions present in these materials, as the rearrangement of ions increases the strength of the field in the device region where reverse-bias breakdown occurs. A further salient feature of the perovskite absorber materials is their large radiative efficiency, which opens up opportunities for luminescent coupling in tandems, but also poses challenges due to the impact on any luminescence-based characterization experiment. In our presentation, we introduce a multi-scale approach to the simulation of all- perovskite tandem modules. To this end, current-voltage characteristics of small-area all- perovskite tandem solar cells are obtained from a calibrated opto-electronic device model using a dedicated drift-diffusion simulation that includes perovskite-specific features such as mobile ions and photon recycling. These JV curves are subsequently
used as local 1D coupling laws connecting the 2D electrodes in a quasi-3D large area finite-element large-area electro-thermal module simulation that then provides the module characteristics under full consideration of spatial variation in active area quality, resistive electrode losses, and module interconnection details.
The simulation framework enables the analysis of losses and optimization of performance on device and module levels, including the quantification of performance
gain due to photon recycling and bifaciality. The impact of non-uniformities in cell-level
performance on the photovoltaic characteristics of monolithically interconnected large-
area all-perovskite tandem modules is quantified, addressing a crucial aspect of the up- scaling challenge for this promising photovoltaic technology.