Understanding Charge Transport in Endohedral Fullerene Single-Crystal Field-Effect Transistors

The encapsulation of nitrogen within C₆₀ forms nonmetallic endohedral fullerene N@C₆₀. Previous calculations show that the encapsulated nitrogen may favor more efficient charge injection and transport under external electric fields when compared to C₆₀, suggesting that N@C₆₀ may be a promising candidate for applications in organic electronic devices. However, owing to difficulties in both synthesis and purification, the potential application of N@C₆₀ under external electric field has not been previously studied experimentally and its intrinsic charge-transport mechanism remains unknown, which hinders more wide applications of endohedral fullerenes in organic electronic devices. Here, we demonstrate the field-effect study and photodetection applications of solution-grown N@C₆₀ single crystals. Organic field-effect transistors (OFETs) based on them exhibit electron mobilities up to 2.23 cm² V^-1 s^-1. Furthermore, the electrical properties show a favorable bandlike charge-transport mechanism from 180 to 300 K, and photodetectors based on them yield a highly sensitive photoconductive property under near-infrared illumination with a responsivity of 177.3 A W^-1. This study, which outlined the intrinsic charge-transport properties of N@C₆₀, should not only enable significant advancements for the high-mobility n-type OFETs and highly sensitive photosensing applications but also provide a reference for studying the fundamental physics of endohedral fullerenes.