All‐SnO₂‐Based Conformal Electron Transport Layer for Efficient Perovskite Solar Cells

The fabrication of high‐performance perovskite solar cells on high‐haze fluorine‐doped tin oxide (FTO) substrates with superior light‐trapping capabilities necessitates a highly conformal electron transport layer at the bottom interface. Herein, a conformal low‐temperature processable all‐SnO 2 ‐based electron transport layer (ETL) is successfully developed on high‐haze FTO by well‐anchoring a polyacrylic acid‐stabilized quantum dot‐SnO 2 layer onto an atomic layer deposited SnO 2 layer with a dense hydroxyl surface. The obtained ETL demonstrates excellent capabilities in simultaneously homogenizing the surface contact potential distribution, blocking hole transport, and suppressing non‐radiative recombination. Consequently, a champion device is achieved that delivers a remarkable power conversion efficiency (PCE) of up to 24.97%, with V OC × FF reaching 87.09% of the Shockley‐Queisser limit at a bandgap of 1.54 eV, which is the highest value among the ALD SnO 2 ‐based PSCs. The homogeneous ETL further enabled the fabrication of a 1 cm 2 PSC with a PCE of 23.18% and only a 10 mV loss in V OC compared to smaller‐area PSCs, showcasing its potential for large‐scale commercial applications.