Organic-inorganic hybrid lead perovskite films are crucial in the perovskite solar cells (PSCs). However, the solution deposition process caused the polycrystalline feature of perovskite films with a large number of...

Perovskite materials have demonstrated many excellent properties in next‐generation photovoltaic devices, but the intrinsic defects and the quality of perovskite film still limit the performance and stability of PSCs. Here, 1,3‐dimethylimidazolium iodide (DMII) ionic liquid was employed as an additive to passivate the various defects and produce the high‐quality perovskite film with enlarged grain sizes. DMII could act as an “ionic stabilizer” for passivating the point defects including the vacancies defects of organic cations and halogen anions of perovskite. At the same time, the extra problematic PbI2 on surfaces and at grain boundaries of the perovskite film could also be reacted by DMII, leading to the reduction of recombination centers and trap states. On the other hand, the DMII ionic liquid with a “Ostwald ripening effect” could retard the crystallization process of perovskite crystals and yield better film quality with higher crystallinity, smoother morphology and larger grains. As a result, the optimal device achieved a champion power conversion efficiency (PCE) of 20.4 %. Particularly, the modified devices demonstrated a significant elevation in open‐circuit voltage from 1.03 to 1.10 V. The hydrophobicity of perovskite films modified by DMII was enhanced and the un‐encapsulated DMII devices retained 91 % of their initial PCE after aging 60 days under 15±5 % relative humidity.

The efficiency of perovskite solar cells (PSCs) has achieved the milestone of 25% with a high speed over the past decade. However, miscellaneous defects at grain boundaries and interfaces have significantly influenced the durability and efficiency of PSCs. In this work, D131 dye, an indoline molecule with a Donor−Acceptor structure, has been introduced into a perovskite precursor as an additive for the first time. The terminal cyanoacrylic acid group of D131 with intense negative charges can interact with Pb 2+ in the precursor to retard crystallization and enhance crystallinity. Moreover, the D131 molecule can stably passivate the undercoordinated Pb 2+ defects at grain boundaries and enhance the thermal and humid stability of perovskite films. As a result, a photovoltaic conversion efficiency (PCE) up to 21.38% (18.55% for 1 cm 2 active area device) has been achieved for the cell with the D131 additive, and the nonencapsulated cell can retain over 81% of its initial PCE after 1100 h of storage (25 °C, 15 ± 5% relative humidity), thus providing a new strategy for durable and high-performance PSCs.

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A rapid and facile synthetic route has been developed to fabricate hierarchically mesoporous TiO2–B, which is composed of nanoparticles and exhibits enhanced reversible capacity and rate capability in lithium ion batteries.