Abstract
The two-step sequential deposition technique reported in the inverted p-i-n configuration to fabricate Sn perovskite solar cells fails in the TiO(2)-based n-i-p configuration since the latter aggravates Sn(2+) oxidation from the SnI(2) nucleation layer upon pore infiltration. However, ambipolar SnO(2) only promotes hole transport in Sn perovskite. Here, we report Cl-doped SnO(2) (Cl:SnO(2)) with surface functionalities using multifunctional polybenzoxazine (p-Benz) to circumvent the SnO(2)/SnI(2) interfacial redox reaction that would otherwise amplify hole extraction. The p-Benz functionalization altered the photoemissive properties of the transparent electrode and introduced a small charge transport resistance against undesirable carrier leakage toward the ETL side by simultaneously enabling contact establishment in the dark. When illuminated, the hole-rich Sn perovskite in contact with the PTAA hole-transport layer allows rapid hole injection, which induces an internal electric field, leading to a functioning planar n-i-p device. By integrating the two-step method in the n-i-p configuration and facilitating selective electron transport in SnO(2), the versatility in device engineering is uncovered.