First Demonstration of Top Contact-Free Perovskite/Silicon Two-Terminal Tandem Solar Cells for Overcoming the Current Density Hurdle

Abstract

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.

Titanium Silicide: A Promising Candidate of Recombination Layer for Perovskite/Tunnel Oxide Passivated Contact Silicon Two-Terminal Tandem Solar Cells

“…The samples were annealed at 600 °C for 30 min in an O 2 atmosphere. The oxidation conditions (temperature and time) were optimized in our previous study Figure a shows that the Ti film was oxidized to TiO 2 (denoted as ox-TiO 2 ) and TiSi 2 was simultaneously formed at the Ti–Si interface.…”

“…The oxidation conditions (temperature and time) were optimized in our previous study. 44 Figure 1 a shows that the Ti film was oxidized to TiO 2 (denoted as ox-TiO 2 ) and TiSi 2 was simultaneously formed at the Ti–Si interface. The ox-TiO 2 and TiSi 2 were used as the ETL and the recombination layer of the perovskite/TOPCon tandem solar cells, respectively.…”