Low-temperature conformal SnO2 coating enables efficient printable mesoscopic perovskite solar cells with industrial scalability

Abstract Hole transport layer-free printable mesoscopic perovskite solar cells (p-MPSCs) employing carbon electrodes offer cost-effective fabrication but face efficiency limitations due to suboptimal charge transport in the TiO 2 -based mesoporous electron transport layer (mp-ETL). Here, we develop a TiO 2 @SnO 2 bilayer mp-ETL for p-MPSCs and obtain encouraging performance enhancement. By performing tailored chemical bath deposition of the preformed triple mesoporous scaffold of TiO 2 ETL/ZrO 2 spacer/carbon electrode rather than the mp-TiO 2 alone, the conformal SnO 2 coating is formed without experiencing high-temperature annealing suffering, thus circumventing associated electronic property degradation. This approach enables selective conformal SnO 2 deposition exclusively on mp-TiO 2 , preventing the formation of undesired current leakage pathway in the spacer. Notably, intentional SnO 2 incorporation in the carbon electrode shows no detrimental effects. The conformal SnO 2 coating successfully improves interfacial energy alignment, suppresses non-radiative recombination, and boosts electron transport. The resulting TiO 2 @SnO 2 p-MPSCs achieve a well improved champion power conversion efficiency (PCE) of 22.5%. The bilayer mp-ETL also demonstrates scalability with 18.8% PCE achieved in 57.33-cm 2 minimodules. Furthermore, encapsulated devices exhibit good operational stability, with 90% efficiency retained after 2000-h maximum power point tracking under continuous illumination at 55 ± 5 °C. This work establishes a practical mp-ETL for high-performance printable perovskite photovoltaics. Graphical Abstract A bilayer mp-ETL of TiO 2 @SnO 2 is developed via low-temperature processing for hole-conductor-free, carbon-based fully printable mesoscopic perovskite solar cells, thereby enabling a PCE of 22.5% and 18.8% for 0.1-cm 2 and 57.33-cm 2 devices.