Understanding the Interfacial Reactions and Band Alignment for Efficient and Stable Perovskite Solar Cells Built on Metal Substrates with Reduced Up-scaling Losses.

Conventional perovskite solar cells (PSC) built on transparent-conductive-oxide (TCO) glass face a fundamental challenge to retain fill factor (FF) for large-area up-scaling due to series resistance loss. Building a perovskite solar cell on metal has the potential to reduce this FF loss and is promising for flexible applications. However, their efficiency and stability lag far behind their TCO counterparts. Herein we report our findings on (i) the complex chemical reactions and degradation-promoting processes at different perovskite/metal (Cu, Au, Ag, and Mo) interfaces, which are closely linked with the inherent stability; and (ii) the interlayer engineering for perovskite/metal interface's band alignment, which plays an essential role in achieving high efficiency. Leveraging these findings, we achieve 21% power-conversion-efficiency (PCE) for 1-cm [ 2 ] perovskite solar cells using a p-i-n top-illumination structure on a molybdenum substrate, the highest reported for a PSC built on metal. Notably, the FF and PCE losses due to area up-scaling are remarkably reduced by one order of magnitude relative to the counterparts on conventional TCO glass, highlighting an alternative pathway for PSC up-scaling and module design. This article is protected by copyright. All rights reserved.