Antisolvent Design for Ambient Air Processing of Perovskite Solar Cells: Polarity, Water Solubility, and Volatility

Antisolvent treatment is extremely effective in achieving high‐efficiency perovskite solar cells. However, in ambient air, conventional low polarity antisolvents such as chlorobenzene or toluene lead to undesirable perovskite film morphologies due to water dissolution. To address this, antisolvents are explored with both low polarity and high water solubility, using Hansen solubility parameters—hydrogen bonding ( δ H ) and polar ( δ P )—as evaluation indices. Solar cells fabricated with various antisolvents show that power conversion efficiency (PCE) improves with increasing δ H / δ P ratio up to 1.3 but declines at higher values, contrary to expectations. This drop in PCE is attributed to the boiling point of the antisolvent: antisolvents with boiling points above the perovskite annealing temperature (120 °C) significantly reduce efficiency. Thus, optimal antisolvents for ambient processing should combine low polarity, high water solubility, and boiling points below the annealing temperature. Alternatively, annealing at temperatures above the boiling point of the antisolvent may also improve the cell performance.