An innovative design for a monolithic perovskite/silicon tandem solar cell, featuring a mesoscopic perovskite top subcell and a high-temperature tolerant homojunction c-Si bottom subcell.

The open‐circuit voltage (VOC) and fill factor are key performance parameters of solar cells, and understanding the underlying mechanisms that limit these parameters in real devices is critical to their optimization. Device modeling is combined with luminescence and cell current–voltage (I–V) measurements to show that carrier transport limitations within the cell can significantly reduce the cell voltage around the maximum power point as well as, under certain conditions, at VOC. An important consequence is that the cell terminal voltage cannot be assumed a priori to be only limited by parasitic recombination. It is demonstrated that luminescence‐based measurements can be used to reconstruct cell I–V curves with removal of any transport limitation effects, which allows the contribution of recombination, shunt resistance, and series resistance on the fill factor to be clarified. Such luminescence‐based measurements allow the contactless characterization of cells and cell precursor structures, and should prove highly valuable as a diagnostic tool for the development of new cell structures and large‐area cells.

Perovskite/silicon 2-terminal tandem cells have made significant advances towards >25% efficiency. Despite this, there is limited understanding of how the optical properties of the materials affect the optical losses within the tandem cell. Using an accurate optical model, we investigate, identify and propose solutions to the optical loss mechanisms inherent in a typical perovskite/silicon 2-terminal tandem cell. The results highlight, firstly, the requirement for low absorption in all layers above the perovskite film, and secondly, the importance of the proper choice of refractive index and thickness of charge transport layers of the perovskite cell, in order to minimize reflection at the interfaces formed by these layers. We demonstrate that the proper choice of these parameters is based on, and can be guided by, basic optics principles which serve as design guidelines. With careful selection of charge transport materials, optimization of the perovskite absorber thickness and the introduction of light trapping within the silicon cell, a matched current of over 20 mA/cm² can be realized, enabling efficiencies greater than 30% using currently available cell processing methods and materials.

No abstract

No abstract