Zirconium acetate stabilized tin dioxide colloidal quantum dots as multifunctional electron transporting layer for efficient and stable perovskite solar cells

The electron transport layer (ETL) is a significant functional layer for enhancing the power conversion efficiency (PCE) and the environmental stability of perovskite solar cells (PSCs). Tin dioxide (SnO2), which has high conductivity and well-matched energy levels with perovskite films, is widely used as one of the most effective ETLs for PSCs. However, it is still a challenge to reduce the energy loss of the SnO2/perovskite interface, which is caused by the SnO2 quantum dots agglomeration due to its disordered surface charge and the SnO2/perovskite interface defects formed during their low-temperature processing. To address this issue, we herein synthesized zirconium acetate stabilized SnO2 (ZAS) quantum dots to terminate the Sn4+ at the SnO2 surface. This suppressed SnO2 agglomeration and formed a uniform film with enhanced conductivity, thereby reducing the SnO2/perovskite interface non-radiative recombination. Furthermore, the C=O and Zr4+ of ZAS could passivate the Pb2+ dangling bonds and uncoordinated I− of the perovskite buried surface, respectively. The energy level of the ZAS ETL showed a favorable match with MAPbI3, accelerating carrier transport and reducing energy loss. As a result, the optimized ZAS-based device achieved an outstanding PCE of 21.13 % and maintained 90 % of its initial PCE under ambient conditions (25 °C, 30–35 % humidity) after 1000 h. This study not only developed a novel ZAS ETL but also inspired us to focus on modifying the surface properties of single SnO2 quantum dots rather than that of the SnO2 film.