10.1021/acsami.5b02456.s001 Tsubasa Mikie Tsubasa Mikie Akinori Saeki Akinori Saeki Naohiko Ikuma Naohiko Ikuma Ken Kokubo Ken Kokubo Shu Seki Shu Seki Hetero Bis-Addition of Spiro-Acetalized or Cyclohexanone Ring to 58π Fullerene Impacts Solubility and Mobility Balance in Polymer Solar Cells American Chemical Society 2015 SCLC circuit voltage SAF 5 monoadduct electrochemical property device PCEs power conversion efficiency LUMO bulk heterojunction 58π Fullerene Impacts Solubility PCBM OPV counter monoadducts CH Voc Cyclohexanone Ring Mobility Balance mobility balance P 3HT 0.80 V 56π fullerenes 2015-06-17 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Hetero_Bis_Addition_of_Spiro_Acetalized_or_Cyclohexanone_Ring_to_58_Fullerene_Impacts_Solubility_and_Mobility_Balance_in_Polymer_Solar_Cells/2205124 Fullerene bis-adducts are increasingly being studied to gain a high open circuit voltage (<i>V</i><sub>oc</sub>) in bulk heterojunction organic photovoltaics (OPVs). We designed and synthesized homo and hetero bis-adduct [60]­fullerenes by combining fused cyclohexanone or a five-membered spiro-acetalized unit (SAF<sub>5</sub>) with 1,2-dihydromethano (CH<sub>2</sub>), indene, or [6,6]-phenyl-C<sub>61</sub>-butyric acid methyl ester (PCBM). These new eight 56π fullerenes showed a rational rise of the lowest unoccupied molecular orbital (LUMO). We perform a systematic study on the electrochemical property, solubility, morphology, and space-charge-limited current (SCLC) mobility. The best power conversion efficiency (PCE) of 4.43% (average, 4.36%) with the <i>V</i><sub>oc</sub> of 0.80 V was obtained for poly­(3-hexylthiophene) (P3HT) blended with SAF<sub>5</sub>/indene hetero bis-adduct, which is a marked advancement in PCE compared to the 0.9% of SAF<sub>5</sub> monoadduct. More importantly, we elucidate an important role of mobility balance between hole and electron that correlates with the device PCEs. Besides, an empirical equation to extrapolate the solubilities of hetero bis-adducts is proposed on the basis of those of counter monoadducts. Our work offers a guide to mitigate barriers for exploring a large number of hetero bis-adduct fullerenes for efficient OPVs.