Efficient and low-temperature processed perovskite solar cells based on a cross-linkable hybrid interlayer

A cross-linkable conjugated polymer, poly[9,9-bis(6′-(N,N-diethylamino)propyl)-fluorene-alt-9,9-bis-(3-ethyl(oxetane-3-ethyloxy)-hexyl)-fluorene] (PFN-OX), was investigated as the n-type interface layer for highly efficient and low-temperature processed planar heterojunction perovskite solar cells. Hybrid composite films consisting of PFN-OX and ZnO nanoparticles were utilized as electron selective layers, and a remarkable power conversion efficiency over 16% was achieved. The cross-linkable PFN-OX provided a robust hybrid composite electron selective layer, which is solvent-resistant during the device fabrication process and results in efficient electron extraction and hole blocking. Meanwhile, time-resolved photoluminescence quenching measurements indicated that the charge separation and collection processes were improved for devices based on PFN-OX:ZnO, in comparison with devices using pure PFN-OX or ZnO. The device stability and the hysteresis effect were also discussed. Moreover, this study introduces the cross-linking concept in perovskite solar cells, which will potentially be an effective strategy for obtaining high performance perovskite solar cells.