Hydrochloride-mediated protonation activation unlocks dual passivation for high-performance perovskite solar cells

Inverted perovskite solar cells (PSCs) suffer from severe non-radiative recombination and poor stability at the buried hole-selective contact. While molecular passivators are extensively employed, conventional designs often overlook the functional role of protonation activation in unlocking their full passivation potential. Here, using 4-hydrazinobenzenesulfonamide (HBS) and its hydrochloride salt (HBSH) as a model pair, we unveil a protonation activation mechanism in which the proton (H + ) derived from the hydrochloride salt protonates the hydrazine group, dramatically enhancing its defect passivation capability. Simultaneously, the chloride anion (Cl − ) serves as an atomic anchor, tethering the protonated molecule firmly to the perovskite lattice to create an ultra-stable buried interface. This dual activation not only accelerates charge extraction and suppresses recombination but also fortifies the interface against degradation. Enabled by this strategy, HBSH-modified inverted PSCs achieve a champion power conversion efficiency of 25.87% and exceptional storage stability, retaining 95% of initial performance after more than 3000 h. This work redefines the role of protonation in interfacial engineering and establishes it as a key design principle for high-performance, long-term stable optoelectronic devices.