Among various types of perovskite‐based tandem solar cells (TSCs), all‐perovskite TSCs are of particular attractiveness for building‐ and vehicle‐integrated photovoltaics, or space energy areas as they can be fabricated on flexible and lightweight substrates with a very high power‐to‐weight ratio. However, the efficiency of flexible all‐perovskite tandems is lagging far behind their rigid counterparts primarily due to the challenges in developing efficient wide‐bandgap (WBG) perovskite solar cells on the flexible substrates as well as their low open‐circuit voltage (VOC). Here, it is reported that the use of self‐assembled monolayers as hole‐selective contact effectively suppresses the interfacial recombination and allows the subsequent uniform growth of a 1.77 eV WBG perovskite with superior optoelectronic quality. In addition, a postdeposition treatment with 2‐thiopheneethylammonium chloride is employed to further suppress the bulk and interfacial recombination, boosting the VOC of the WBG top cell to 1.29 V. Based on this, the first proof‐of‐concept four‐terminal all‐perovskite flexible TSC with a power conversion efficiency of 22.6% is presented. When integrating into two‐terminal flexible tandems, 23.8% flexible all‐perovskite TSCs with a superior VOC of 2.1 V is achieved, which is on par with the VOC reported on the 28% all‐perovskite tandems grown on the rigid substrate.

Perovskite Solar Cells In article number 2202438, Cong Chen, Dewei Zhao, Fan Fu, and co‐workers report 15.1% flexible near‐infrared transparent wide‐bandgap (1.77 eV) perovskite solar cells with a low open‐circuit voltage–deficit of 480 mV. When paired with flexible, narrow‐bandgap (1.24 eV) perovskite solar cells, they demonstrate a 23.8% flexible all‐perovskite tandem solar cell with a superior open‐circuit voltage of 2.1 V.

Lithiated Nb, Al, or Ti metal oxide interlayers improve the LiCoO2/LLZO interface, whereby the Li–Nb–O interlayer exhibits the highest performance.

The power capability of Li-ion batteries has become increasingly limiting for the electrification of transport on land and in the air. The specific power of Li-ion batteries is restricted to a few thousand W/kg due to the required cathode thickness of a few tens of micrometers. We present a new design of monolithically-stacked thin-film cells that has the potential to increase the power ten-fold. We demonstrate an experimental proof-of-concept consisting of two monolithically stacked thin-film cells. Each cell consists of a silicon anode, a solid-oxide electrolyte, and a lithium cobalt oxide cathode. The battery can be cycled for more than 300 cycles between 6 and 8 V. Using a thermo-electric model, we predict that stacked thin-film batteries can achieve specific energies >250 Wh/kg at C-rates above 60, resulting in a specific power of tens of kW/kg needed for high-end mobile applications such as drones, robots, and eVTOLs.

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