In the quest for advancing photovoltaic efficiency, the adoption of multijunction solar cell architectures has emerged as a promising approach. Perovskite/silicon double-junction solar cells have already achieved efficiencies surpassing 33%, exceeding the theoretical efficiency limit for single-junction devices. To enhance efficiency even further, exploring perovskite/perovskite/silicon (PPS) triple-junction solar cells seems a logical next step, as they offer the potential to further reduce thermalization losses and achieve even higher efficiencies. This study delves into the potential of various configurations of PPS modules, exploring different subcell interconnections. Initially, we present an optoelectrical model to simulate the performance of these devices, incorporating both luminescence coupling and cell-to-module losses. This enables us to optimize the bandgap energy of the top and middle perovskite subcells under both standard test conditions (STC) and outdoor conditions. Our analysis reveals that the addition of a perovskite subcell can improve the STC efficiency up to 9%–13%. This gain in STC performance also translates into a similar gain in energy yield, meaning that triple-junction devices produce 8%–14% more electricity than their double-junction reference devices.

We investigate gentle front side textures for perovskite/silicon tandem solar cells. These textures enhance the absorption of sunlight, yet are sufficiently gentle to allow deposition of an efficient perovskite top cell. We present a tandem solar cell with such gentle texture, fabricated by Kaneka corporation, with an efficiency as high as 28.6%. We perform an extensive ray-optics study, exploring non-conformal textures at the front and rear side of the perovskite layer. Our results reveal that a gentle texture with steepness of only 23° can be more optically efficient than conventional textures with more than double that steepness. We also show that the observed anti-reflective effect of such gentle textures is not based a double bounce, but on light trapping by total internal reflection. As a result, the optical effects of the encapsulation layers play an important role, and have to be accounted for when evaluating the texture design for perovskite/silicon tandems.

We use simulations to optimize perovskite/silicon tandem solar cells in a novel three-terminal configuration, with one terminal at the front and two at the rear. We consider configurations in which the top cell has either the inverted or the same polarity as the bottom cell. Our goal is to minimize the optical losses, to compare the performance of both configurations and to determine the realistically achievable efficiency. Optical simulations show that if the hole-transporting material is in front of the perovskite, it gives rise to parasitic absorption losses. If it is behind the perovskite, these losses are avoided, however, at the cost of increased reflection losses. We systematically minimize these reflection losses. This increases the tandem's total implied photocurrent density from 34.4 to 41.1 mA/cm ² . To determine the corresponding power conversion efficiency of these three-terminal tandems, electrical circuit simulations are performed based on existing 22.7% efficient perovskite and 24.9% efficient silicon cells. These simulations show that tandem efficiencies up to 32.0% can be obtained.

We present a new version of our optical model for solar cell simulation: GenPro4. Its working principles are briefly explained. The model is suitable for quickly and accurately simulating a wide range of wafer-based and thin-film solar cells. Especially adjusting layer thicknesses to match the currents in multijunction devices can be done with a minimum of computational cost. To illustrate this, a triple junction thin-film silicon solar cell is simulated. The simulation results show very good agreement with external quantum efficiency measurements. The application of an MgF₂ antireflective coating or an antireflective foil with pyramid texture is considered. Their effects on the implied photocurrents of top, middle, and bottom cells are investigated in detail.

In a monolithic perovskite/c-Si tandem device, the perovskite top cell has to be deposited onto a flat c-Si bottom cell without anti-reflective front side texture, to avoid fabrication issues. We use optical simulations to analyze the reflection losses that this induces. We then systematically minimize these losses by introducing surface textures in combination with a so-called burial layer to keep the perovskite top cell flat. Optical simulations show that, even with a flat top cell, the monolithic perovskite/c-Si tandem device can reach a matched photocurrent density as high as 19.57 mA/cm².