Multi-site passivation-based antisolvent additive engineering with gradient distribution for superior triple cation P-I-N perovskite solar cells

The large number of diverse types of trap sites on the surface and inside perovskite substantially restrict the production of highly efficient and stable perovskite solar cells (PSCs). Therefore, it is essential to fabricate high-quality perovskite films via the passivation of multi-site defects at the surface and grain boundaries through modulating perovskite crystallization and passivating as many defects of perovskite films as possible. Although many passivation molecules have been reported, it is still necessary to develop a deeper understanding of the various functional group effects as well as the different passivation strategies that can be used to introduce additives. Here, to confirm the effects of functional groups, the four acrylate-based molecules that contain carbonyl (CO), hydroxyl (–OH), alkoxy (–O–CH2), or aromatic functional group are used as additives for antisolvent additive engineering (AAE). We then systematically investigate the effects of the passivation molecules on perovskite films and devices. The use of the optimum multi-functional additive, 3-Phenoxy-2-hydroxypropyl acrylate (PHA), enables a champion power conversion efficiency (PCE) of 20.72% as well as higher ambient air stability, as it retains over 51% of its initial PCE after 129 days. We also find that, compared to other representative passivation techniques, AAE containing passivation molecules leads to better perovskite films with a lower defect density and better photovoltaic performance. Consequently, the multi-type defects caused by the ionic properties of perovskite are substantially reduced due to the synergetic effects of the functional groups; further, the AAE approach has also proven to be a more promising way to obtain high-quality perovskite films corresponding to high-efficiency PSCs.