In this work, nickel silicide was applied to tandem solar cells as an interlayer. By the process of thermal evaporation, a layer of NiOx, hole transport layer (HTL) was deposited on n+ poly-Si layer directly. Nickel silicide was simultaneously formed by nickel diffusion from NiOx to n+ poly-Si layer during the deposition and annealing process. The I–V characteristics of NiOx/n+ poly-Si contact with nickel silicide showed ohmic contact and low contact resistivity. This structure is expected to be more advantageous for electrical connection between perovskite top cell and TOPCon bottom cell compared to the NiOx/TCO/n+ poly-Si structure showing Schottky contact. Furthermore, nickel silicide and Ni-deficient NiOx thin film formed by diffusion of nickel can improve the fill factor of the two sub cells. These results imply the potential of a NiOx/nickel silicide/n+ poly-Si structure as a perovskite/silicon tandem solar cell interlayer.

Monolithic perovskite–silicon tandem solar cells with MoOx hole selective contact silicon bottom solar cells show a power conversion efficiency of 8%. A thin 15 nm-thick MoOx contact to n-type Si was used instead of a standard p+ emitter to collect holes and the SiOx/n+ poly-Si structure was deposited on the other side of the device for direct tunneling of electrons and this silicon bottom cell structure shows ~15% of power conversion efficiency. With this bottom carrier selective silicon cell, tin oxide, and subsequent perovskite structure were deposited to fabricate monolithic tandem solar cells. Monolithic tandem structure without ITO interlayer was also compared to confirm the role of MoOx in tandem cells and this tandem structure shows the power conversion efficiency of 3.3%. This research has confirmed that the MoOx layer simultaneously acts as a passivation layer and a hole collecting layer in this tandem structure.

Current density plays a substantial role in monolithic tandem solar cells; however, it is difficult to control because subcells and auxiliary layers are stacked and serially connected vertically to obtain higher voltages. The vertically stacked structure intrinsically triggers inevitable parasitic absorption. In current typical perovskite/silicon two-terminal (2-T) tandem solar cells, 5−10 layers are placed on the light path, even though they are not current generating layers. These layers usually include transparent window layers, buffer layers, carrier extraction layers, and recombination layers. Therefore, the development of top contact-free architectures to reduce parasitic absorption in 2-T tandem solar cells is required for achieving high efficiency. In this study, a top contact-free perovskite/silicon 2-T tandem solar cell with quasi-interdigitated intermediate electrodes (Q-IDIEs) is reported for the first time. Several layers placed above the perovskite layer in conventional devices are relocated to the backside of the perovskite. The Q-IDIE, composed of a patterned Ni/NiO X shell above the full-deposited TiO 2 , was fabricated by the following processes: photolithography, lift-off, and oxidation. The device results in 4.23% efficiency with an open-circuit voltage of 1.54 V. This tandem architecture is expected to be a breakthrough for overcoming the theoretical efficiency limit of single-junction solar cells with further optimization.

Perovskite Solar Cells In article number http://doi.wiley.com/10.1002/solr.202300214, Kang, Lee, and co‐workers presented a novel approach for fabricating perovskite films using a sputtering process. They applied post‐processes to enhance the film properties and the electrical characteristics of perovskite solar cells. These processes enable the deposition of uniform perovskite films on large‐area textured silicon substrates, opening new possibilities for efficient solar energy conversion.

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