Carbon-based mesoscopic perovskite solar cells (MPSCs) are becoming one of the most competitive photovoltaic technologies owing to their lower manufacturing cost and excellent stability. In this work, methylammonium acetate (MAAc), an ionic liquid additive, is added into methylammonium lead triiodide (MAPbI 3 ) perovskite and is used to fabricate high-performance MPSCs. Systematic and detailed studies have shown that the MAAc interacts with PbI 2 preferentially to form a MAPbI 3−x (Ac) x intermediate phase that can effectively control the crystallization kinetics of MAPbI 3 in the triple-mesoscopic layer. MAPbI 3 films with an appropriate amount of MAAc exhibit higher crystallinity, lower defect density, and dense pore filling, which effectively reduce carrier nonradiative recombination loss in MPSCs. As a result, a champion power conversion efficiency (PCE) of 13.54% is obtained based on the optimized MAAc-engineered MPSCs. The PCE is 24% higher than 10.90% of the control devices. Moreover, unencapsulated MAAc-engineered MPSCs retain 90% of their initial PCE after being stored in the dark for 50 days under ambient atmosphere, which demonstrates much better air stability than control devices. This work provides an effective strategy for developing efficient and stable carbon-based MPSCs with an eco-friendly ionic liquid additive.

Printable mesoscopic perovskite solar cells (p-MPSCs) have received extensive attention from researchers and entrepreneurs worldwide because of their low cost, simple manufacturing process, and feasible fabricate in air. However, the wide application of p-MPSCs is limited by their relatively low power conversion efficiency (PCE). Herein, we propose a performance enhancement strategy for p-MPSCs by introducing 1-benzyl-3-methylimidazolium chloride (BZMIMCl) ionic liquid into a perovskite precursor. The BZMIMCl ionic liquid optimized the crystallization of perovskite films, modulated the energy band alignment of the perovskite, and improved carrier transport, thereby enhancing the overall photovoltaic parameters and stability of p-MPSCs. The champion PCE of the BZMIMCl-optimized device was 16.06%. Moreover, the unencapsulated p-MPSCs containing BZMIMCl maintained ∼89.6% of its maximum value after being stored for 60 days in an atmospheric environment (25 ± 5 °C @ 50 ± 5% RH, in the dark). This work further promotes the application of ionic liquids in the development of efficient p-MPSCs.

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Excellent stability, low costs, and printability are the most significant features of printable mesoscopic perovskite solar cells (p‐MPSCs). However, the introduction of carbon electrodes reduces the cost of production while causing severe voltage losses within the p‐MPSCs. Herein, formamidine (FA), cesium, and rubidium are selected as A‐site cations (or cationic groups) in perovskite films, and nicotinamide (3‐pyridine formamide, NTM) is introduced as an additive to modify the perovskite films for the preparation of p‐MPSCs. The introduction of NTM can effectively passivate the crystal defects of perovskite films filled in the triple mesopores (mesoscopic TiO2/ZrO2/C), which enhances the pore filling and improves the carrier transportation and extraction efficiency. In addition, the amide group can effectively enhance the work function of the perovskite films and further increase the open‐circuit voltage (VOC) of the p‐MPSCs. Consequently, major benefitting from the significant increase in VOC (from 880 to 970 mV), the power conversion efficiency (PCE) of the NTM‐modified p‐MPSCs is improved up to 16.36%, which is nearly 20% improvement compared with the 14.36% of the control devices. In addition, the unencapsulated modified NTM‐modified (FA)CsRbPbI3 p‐MPSCs show excellent stability in air by maintaining 85% of the initial PCE after 90 days of storage.

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