Fully High‐Temperature‐Processed SnO 2 as Blocking Layer and Scaffold for Efficient, Stable, and Hysteresis‐Free Mesoporous Perovskite Solar Cells

Abstract Planar perovskite solar cells (PSCs) based on low‐temperature‐processed (LTP) SnO 2 have demonstrated excellent photovoltaic properties duo to the high electron mobility, wide bandgap, and suitable band energy alignment of LTP SnO 2 . However, planar PSCs or mesoporous (mp) PSCs based on high‐temperature‐processed (HTP) SnO 2 show much degraded performance. Here, a new strategy with fully HTP Mg‐doped quantum dot SnO 2 as blocking layer (bl) and a quite thin SnO 2 nanoparticle as mp layer are developed. The performances of both planar and mp PSCs has been greatly improved. The use of Mg‐SnO 2 in planar PSCs yields a high‐stabilized power conversion efficiency (PCE) of close to 17%. The champion of mp cells exhibits hysteresis free and stable performance with a high‐stabilized PCE of 19.12%. The inclusion of thin mp SnO 2 in PSCs not only plays a role of an energy bridge, facilitating electrons transfer from perovskite to SnO 2 bl, but also enhances the contact area of SnO 2 with perovskite absorber. Impedance analysis suggests that the thin mp layer is an “active scaffold” selectively collecting electrons from perovskite and can eliminate hysteresis and effectively suppress recombination. This is an inspiring advance toward high‐performance PSCs with HTP mp SnO 2 .