A Core@Dual-Shell Nanostructured SnO2 to Modulate the Buried Interfaces Toward Stable Perovskite Solar Cells With Minimized Energy Losses

Investigation and optimization of the buried interfaces are crucial for further improving the efficiency and stability of perovskite solar cells (PSCs). In this work, a general route to modify the interfaces of electron conductor is strategically developed via introducing a well-designed core@dual-shell structure based on SnO2 nanoparticles grafted by potassium thiocyanate (KSCN) and polyethylene oxide (PEO). This graded bimolecular strategy is desired as it efficiently decouples the processes of defect healing and crystallization engineering. Synergistic effects of KSCN and PEO lead to superior structural uniformity at the buried interfaces, enhanced charge collection, as well as the suppressed carrier recombination. Consequently, a significant increase of efficiency from 20.0% to 23.01% is achieved, accompanied by a remarkable open-circuit voltage of 1.19 V and extremely low energy losses down to 0.4 eV. Moreover, this interfacial configuration enables the unencapsulated devices to have greatly improved performance longevity by retaining 87% of initial power after 5112 h storage in air, as well as strong mechanical endurance by maintaining over 80% of initial efficiency after 4700 bending cycles at a curvature radius of 5 mm for flexible devices. This work offers an effective and generally applicable approach for engineering the nanostructured interface to realize stable and efficient PSCs.