%0 Journal Article %A Zhong, Yufei %A Izawa, Seiichiro %A Hashimoto, Kazuhito %A Tajima, Keisuke %A Koganezawa, Tomoyuki %A Yoshida, Hiroyuki %D 2015 %T Crystallization-Induced Energy Level Change of [6,6]-Phenyl‑C61-Butyric Acid Methyl Ester (PCBM) Film: Impact of Electronic Polarization Energy %U https://acs.figshare.com/articles/journal_contribution/Crystallization_Induced_Energy_Level_Change_of_6_6_Phenyl_C_sub_61_sub_Butyric_Acid_Methyl_Ester_PCBM_Film_Impact_of_Electronic_Polarization_Energy/2218096 %R 10.1021/jp506296j.s001 %2 https://ndownloader.figshare.com/files/3853828 %K polarization energy %K PCBM molecule %K photoelectron spectroscopy %K Electronic Polarization EnergyThe effect %K Methyl Ester %K photoemission spectroscopy %K IP %K EA %K film thickness %K 0.1 eV %K energy levels %K electron affinity %K Precise measurements %K annealing %K band gap %X The effect of thermal annealing on the energy levels of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) films was investigated using ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and low-energy inverse photoemission spectroscopy. We observed that thermal annealing at 150 °C induces reductions of both the ionization potential (IP) and the electron affinity (EA) with a narrowing of the band gap by 0.1 eV. These changes are associated with crystallization and a 2.54% reduction in the film thickness. Precise measurements of both the IP and EA enabled an evaluation of the effects of the electronic polarization energy in a model based on the charge localized in a single PCBM molecule. %I ACS Publications