Nonionic Sc₃N@C₈₀ Dopant for Efficient and Stable Halide Perovskite Photovoltaics

One major challenge in the commercialization of halide perovskite solar cells is the device instability against moisture. Efficient perovskite solar cells usually incorporate the ionic dopants within the charge transfer material to secure their electrical conductivity. Typical ionic dopants are hygroscopic, resulting in significant moisture adsorption and accelerated perovskite degradation. Herein, we report a nonionic dopant, Sc₃N@C₈₀, consisting of a hydrophobic fullerene cage that encapsulates the metal salt to achieve a moisture resistive and highly electrically conductive hole transfer layer (HTL). The direct electronic transaction between Sc₃N@C₈₀ and spiro-OMeTAD renders a drastically improved conductivity and a lower Fermi-level of the HTL to minimize the Schottky barrier. The hydrophobicity of Sc₃N@C₈₀ also decreases the moisture wettability. Perovskite solar cells using the Sc₃N@C₈₀-doped HTL exhibit an efficiency surge from 18.15 to 20.77% (champion cell exhibiting 21.09%) and improved device stability (survival efficiency over 17% after continuous illumination for 800 h). The bifunctional hydrophobic Sc₃N@C₈₀ dopant provides a pathway toward efficient and stable perovskite photovoltaics.