Side-chain effects on electronic structure and molecular stacking arrangement of PCBM spin-coated films

► Verification of energy symmetry breaking of C60 π-orbitals due to side chain. ► Angle-dependent π∗ feature revealing asymmetrical orbital distribution of PCBM. ► The presence of partially lifted LUMO degeneracy around the attachment point. ► Ordered molecular stacking structures determined from X-ray polarization dependence.