Li@C60 endohedral fullerene as a supraatomic dopant for C60 electron-transporting layers promoting the efficiency of perovskite solar cells

C60:Li@C60 hybrid n-type semiconducting films were first fabricated. The Fermi level of 1% Li@C60-added C60 films was determined to be −4.52 eV, which was 0.12 eV higher than that of pristine C60 films. A fraction of Li@C60 is distributed uniformly within the C60 film. Its application in PSCs was demonstrated, in which the addition of Li@C60 into a C60 film improved the device performance.