A Polymer Defect Passivator for Efficient Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells

Abstract Due to the low cost and excellent potential for mass production, printable mesoscopic perovskite solar cells (p‐MPSCs) have drawn a lot of attention among other device structures. However, the low open‐circuit voltage (V_OC) of such devices restricts their power conversion efficiency (PCE). This limitation is brought by the high defect density at perovskite grain boundaries in the mesoporous scaffold, which results in severe nonradiative recombination and is detrimental to the V_OC. To improve the perovskite crystallization process, passivate the perovskite defects, and enhance the PCE, additive engineering is an effective way. Herein, a polymeric Lewis base polysuccinimide (PSI) is added to the perovskite precursor solution as an additive. It improves the perovskite crystallinity and its carbonyl groups strongly coordinate with Pb²⁺, which can effectively passivate defects. Additionally, compared with its monomer, succinimide (SI), PSI serves as a better defect passivator because the long‐chained macromolecule can be firmly anchored on those defect sites and form a stronger interaction with perovskite grains. As a result, the champion device has a PCE of 18.84%, and the V_OC rises from 973 to 1030 mV. This study offers a new strategy for fabricating efficient p‐MPSCs.