Functionalized Fullerenes in Perovskite Photovoltaic Devices

Perovskite photovoltaic (PV) technology offers outstanding advantages, making it a research hotspot for next-generation solar cells and securing a key strategic position in the field of clean energy. Within this technological framework, fullerenes have become indispensable key functional components in perovskite PV devices, attracting widespread attention from both academia and industry due to their high electron affinity, three-dimensional electron transport properties, and excellent defect-passivation capability. However, the application of pristine fullerene C60 in perovskite solar cells (PSCs) is still hindered by several limitations, including poor solubility in common solvents, suboptimal energy level alignment with different perovskites, and insufficient passivation of defects at the perovskite interfaces. These issues restrict further improvements in both device efficiency and long-term operational stability. To address these bottlenecks, various solution strategies have been reported from different perspectives. Nevertheless, a systematic view spanning from molecular design to device integration is still lacking. Driven by the rapid developments of PSCs, the core contribution of our team lies in the design and synthesis of a series of functionalized fullerene derivatives through precise molecular engineering strategies, and their systematic integration as multifunctional modules into different critical interfaces and the bulk phase of perovskite PV devices. In this Account, we systematically summarize the principles of molecular design, chemically tailored synthetic strategies to meet diverse functional requirements, multiscale integration methodologies within device architectures, and the underlying mechanisms that contribute to the comprehensive enhancement of device performance. Particular emphasis is placed on elucidating how functionalization influences critical processes such as film morphology, electron transport characteristics, charge recombination suppression, and ion migration inhibition, thereby revealing the intrinsic rules by which these materials govern device efficiency and stability. Furthermore, we discuss the potential of emerging endohedrally functionalized metallofullerenes, along with current challenges in the field, including multiple integrations with tandem/flexible/commercial-size devices, the synthetic complexity and cost control of fullerenes, and their application possibility in emerging lead-free PSCs, which seeks to elucidate the multifaceted roles of exo- and endofunctionalized fullerenes in PSCs. Finally, we present an outlook on future research directions for functionalized fullerenes, aiming to drive progress toward high-efficiency, stable, and industrially scalable PSCs. We believe this Account will attract broad interest from researchers in the fields of perovskite photovoltaics, organic electronics, and carbon nanomaterials science, thereby promoting fundamental research and industrial applications of functional carbon nanomaterials in emerging PV technologies.