Enhancement in charge extraction and moisture stability of perovskite solar cell via infiltration of charge transport material in grain boundaries

Perovskite solar cells (PeSCs) attract significant attention owing to their numerous advantages such as superior optical/electrical properties and solution processability. However, the existence of defects in the grain boundaries still prevents high performance and stable PeSCs. Here, we present a simple yet effective momentary spinning (MS) method for passivating defect sites in the grain boundaries of PeSCs. By applying the MS method to the perovskite active layer, we achieve infiltration of p-type hole transporting materials (HTMs) with selective hole transport into grain boundaries, thereby reducing leakage current, suppressing nonradiative recombination loss, and achieving efficient hole extraction. The MS-fabricated PeSCs remarkably enhance device performance, displaying higher short-circuit current (J_sc), open-circuit voltage (V_oc), and fill factor (FF) than the conventional spin-coating (SC) devices. The best device exhibits a J_sc of 23.2 mA cm⁻², a V_oc of 0.99 V, and an FF of 0.81, yielding a power conversion efficiency (PCE) of 18.6%. In addition, passivating hydrophilic grain boundaries with hydrophobic HTM improves the moisture stability of the device. When device performance is monitored for over 20 days of storage, the MS device exhibits improved stability with over 80% of the initial PCE compared to the SC device with only 50%.