Stabilizing Grain Boundaries by Flexible Bidirectional Multisite Hydrazide Cations toward High-Performance Inverted Perovskite Solar Cells

The grain boundary instability induced by defects and tensible strain impedes the realization of high-performance inverted perovskite solar cells (PSCs). Here, we propose a flexible bidirectional multisite additive strategy to stabilize perovskite. (6-(2,5-Dioxo-2,5-dihydro-1H-pyrror-1-yl) hexanehydrazide hydrochloride (PHHCl) with a hydrazide cation, three carbonyl groups, and a flexible alkyl chain is leveraged to manipulate the GBs of perovskite. The multiple functional groups in PHH+ synergistically participate in passivating various charged defects via rich chemical bonding modes. The bidirectional distribution of functional groups and molecular flexibility can not only enhance the defect passivation capability of PHH+ but also realize chemical bridging between neighboring perovskite grains. The PHHCl-modulated 1.55 eV inverted PSC accomplishes a certified power conversion efficiency (PCE) of 27.0%, accompanied by exceptional operational stability with a T90 lifetime of 1084 h under continuous maximum power point tracking. Moreover, the PHHCl-modified 1.78 eV and 1.68 eV PSCs yield PCEs of 20.3% and 23.5%, respectively.