Fullerene derivatives and perovskite solar batteries

A perovskite solar battery comprising:

• conductive glass;
• a hole transport layer;
• a perovskite layer;
• and
• an electron transport layer comprising a fullerene derivative and a back electrode, the fullerene derivative having a C60 fullerene group and a group of a compound of formula (1), a compound of formula (2), and/or a compound of formula (3) attached to the C60 fullerene group, wherein structural formulas of the compounds of formula (1), formula (2), and formula (3) are as follows:
• wherein:
• R1, R4, and R7 are each independently selected from R′, a phenyl group, a naphthyl group, a biphenyl group, R′ substituted with a halogen, a phenyl group substituted with a halogen, a naphthyl group substituted with a halogen, a biphenyl group substituted with a halogen, a nitrogen-containing group, R′ substituted with a nitrogen-containing group, a phenyl group substituted with a nitrogen-containing group, a naphthyl group substituted with a nitrogen-containing group, or a biphenyl group substituted with a nitrogen-containing group;
• R2, R5, and R8 are each independently selected from hydrogen or R′;
• R3, R6, and R9 are each independently selected from hydrogen, halogen, —O—R, a nitrogen-containing group, —OH, —OR, —NHCOR, —OCOR, —R, —CH2COOH, a phenyl group, or a naphthyl group;
• the nitrogen-containing group is -N(R)2, —NHR, —NH2, a trimethylamine group, a triethylamine group, or a tripropylamine group;
• R′ is an alkyl group with 1-5 carbon atoms;
• R is an alkyl group with 1-10 carbon atoms;
• and
• n1, n2, n3, m1, m2, and m3 are each independently an integer in the range of 0-10, n1 + m1 ≤ 10, n2 + m2 ≤ 10, and n3 + m3 ≤ 10.