The passivation of perovskite bulk and heterointerface defects is one of the most significant ways to enhance the efficiency and operational stability of perovskite solar cells (PSCs). So far, ammonium‐based alkylamine halides have been considered as effective passivation materials to reduce defects of the perovskite absorber layer. Herein, roles of long‐chain alkylamine ligands (LALs) in triple‐halide perovskites are systematically studied for achieving efficient NiOx‐based inverted PSCs. Two kinds of LALs oleylammonium (OAm) and phenethylammonium (PEA), as perovskite bulk and interface passivation agents, respectively, are introduced. It is found that both OAm and PEA ligands cannot only assist their crystal growth with vertical orientation, but also suppress triple‐halide perovskite bulk and interface defects. As precursor additives, OAm ligands can be used as organic spacers to assist the generation of the 2D@3D perovskite bulk crystals. 2D@3D/2D perovskite heterostructures are further formed when the 2D@3D perovskite bulk film is post‐treated by PEA ligands. As a result, such strategies enable hysteresis‐free and highly efficient NiOx‐based triple‐halide inverted PSCs.
NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost, highly efficient and stable next-generation photovoltaics. However, the presence of energy-level mismatch and contact-interface defects between hole-selective contacts (HSCs) and perovskite-active layer (PAL) still limits device efficiency improvement. Here, we report a graded configuration based on both interface-cascaded structures and p-type molecule-doped composites with two-/three-dimensional formamidinium-based triple-halide perovskites. We find that the interface defects-induced non-radiative recombination presented at HSCs/PAL interfaces is remarkably suppressed because of efficient hole extraction and transport. Moreover, a strong chemical interaction, halogen bonding and coordination bonding are found in the molecule-doped perovskite composites, which significantly suppress the formation of halide vacancy and parasitic metallic lead. As a result, NiOx-based inverted PSCs present a power-conversion-efficiency over 23% with a high fill factor of 0.84 and open-circuit voltage of 1.162 V, which are comparable to the best reported around 1.56-electron volt bandgap perovskites. Furthermore, devices with encapsulation present high operational stability over 1,200 h during T90 lifetime measurement (the time as a function of PCE decreases to 90% of its initial value) under 1-sun illumination in ambient-air conditions.
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