Flexible perovskite solar cells (F-PSCs) have attracted enormous attentions in portable and wearable electronics due to low-cost and high power-per-weight. However, there is still much room towards the advancement in...

With the steady industrialization process of the perovskite solar cells (PSCs), the toxicity of the used solvents has become a pivotal issue that needs to be addressed. Especially, the usage of N,N-dimethylformamide (DMF) solvent would pose serious environmental and health concerns. Herein, we have reported a nontoxic solvent N-formylmorpholine (NFM) to replace the toxic DMF and have achieved a higher PCE of 22.78% compared to 21.97% when DMF was adopted. Moreover, with NFM, a widened antisolvent processing window was observed, facilitating the fabrication of PSCs with high reproducibility. This solvent engineering strategy offers an important solution to prepare eco-friendly, efficient, and stable perovskite solar cells.

The pinhole‐free and defect‐less perovskite film is crucial for achieving high efficiency and stable perovskite solar cells (PSCs), which can be prepared by widely used anti‐solvent crystallization strategies. However, the involvement of anti‐solvent requires precise control and inevitably brings toxicity in fabrication procedures, which limits its large‐scale industrial application. In this work, a facile and effective co‐solvent engineering strategy is introduced to obtain high‐ quality perovskite film while avoiding the usage of anti‐solvent. The uniform and compact perovskite polycrystalline films have been fabricated through the addition of co‐solvent that owns strong coordination capacity with perovskite components , meanwhile possessing the weaker interaction with main solvent . With those strategies, a champion power conversion efficiency (PCE) of 22% has been achieved with the optimal co‐solvent, N‐methylpyrrolidone (NMP) and without usage of anti‐solvent. Subsequently, PSCs based on NMP show high repeatability and good shelf stability (80% PCE remains after storing in ambient condition for 30 days). Finally, the perovskite solar module (5 × 5 cm) with 7 subcells connects in series yielding champion PCE of 16.54%. This strategy provides a general guidance of co‐solvent selection for PSCs based on anti‐solvent free technology and promotes commercial application of PSCs.

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