Metal-organic frameworks with mixed-ligands strategy as heterogeneous nucleation center to assist crystallization for efficient and stable perovskite solar cells

Abstract

Deep-level defects and random oriented configuration in perovskite crystallization process would cause the nonradiative recombination and further affect the performance of perovskite solar cells (PSCs). Herein, two metal-organic frameworks (MOFs) with tunable Lewis-base passivation sites have been constructed (Cd-Httb and Cd-Httb-BDC, Httb = 5-(4-(1H-1,2,4-triazole-1-yl)benzyl)-1h-tetrazole, BDC = 1,4-dicarboxybenzene) to eliminate deep-level defects and simultaneously as nanostructured heterogeneous nucleation seed to assist the growth of large-grained perovskite films. Compared with the control and Cd-Httb, Cd-Httb-BDC designed with mix-ligands strategy exhibited the enhanced inducted effect on the crystallization and nucleation of high-quality perovskite films during annealing process. Consequently, the resultant Cd-Httb-BDC-modified device achieved higher power conversion efficiency (PCE) (22.18%) than the control (20.89%) and Cd-Httb (21.56%). Meanwhile, the unencapsulated Cd-Httb-BDC-modified device still maintained 90% of initial PCE after 1500 h in ambient conditions and exhibited enhanced thermal stability (85 °C in N2 atmosphere). This work presented a successful example of mix-ligands strategy on construction of high-quality MOF-assisted perovskite films for high-efficient and stable PSCs.