AbstractThe benchmark tin oxide (SnO₂) electron transporting layers (ETLs) have enabled remarkable progress in planar perovskite solar cell (PSCs). However, the energy loss is still a challenge due to the lack of “hidden interface” control. We report a novel ligand-tailored ultrafine SnO₂ quantum dots (QDs) via a facile rapid room temperature synthesis. Importantly, the ligand-tailored SnO₂ QDs ETL with multi-functional terminal groups in situ refines the buried interfaces with both the perovskite and transparent electrode via enhanced interface binding and perovskite passivation. These novel ETLs induce synergistic effects of physical and chemical interfacial modulation and preferred perovskite crystallization-directing, delivering reduced interface defects, suppressed non-radiative recombination and elongated charge carrier lifetime. Power conversion efficiency (PCE) of 23.02% (0.04 cm²) and 21.6% (0.98 cm², V_OC loss: 0.336 V) have been achieved for the blade-coated PSCs (1.54 eV E_g) with our new ETLs, representing a record for SnO₂ based blade-coated PSCs. Moreover, a substantially enhanced PCE (V_OC) from 20.4% (1.15 V) to 22.8% (1.24 V, 90 mV higher V_OC, 0.04 cm² device) in the blade-coated 1.61 eV PSCs system, via replacing the benchmark commercial colloidal SnO₂ with our new ETLs.