One-Stone-For-Three-Birds Strategy Using a Fullerene Modifier for Efficient and Stable Inverted Perovskite Solar Cells.

The electron extraction from perovskite/C interface plays a crucial role in influencing the photovoltaic performance of inverted perovskite solar cells (PSCs). Here, we develop a one-stone-for-three-birds strategy via employing a novel fullerene derivative bearing triple methyl acrylate groups (denoted as C-TMA) as a multifunctional interfacial layer to optimize electron extraction at the perovskite/C interface. It is found that the C-TMA not only passivates surface defects of perovskite via coordination interactions between C=O groups and Pb cations but also bridge electron transfer between perovskite and C. Moreover, it effectively induces the secondary grain growth of the perovskite film through strong bonding effect, and this phenomenon has never been observed in prior art reports on fullerene related studies. The combination of the above three upgrades enables improved perovskite film quality with increased grain size and enhanced crystallinity. With these advantages, C-TMA treated PSC devices exhibit a much higher power conversion efficiency (PCE) of 24.89 % than the control devices (23.66 %). Besides, C-TMA benefits improved thermal stability of PSC devices, retaining over 90 % of its initial efficiency after aging at 85 °C for 1200 h, primarily due to the reinforced interfacial interactions and improved perovskite film quality.