We have studied the electronic structure of [6,6]-phenyl-C61-butyric-acid-methyl-ester （PCBM） using synchrotron radiation photoelectron spectroscopy （PES） measurements and first-principles calculations. The PES sp...We have studied the electronic structure of [6,6]-phenyl-C61-butyric-acid-methyl-ester （PCBM） using synchrotron radiation photoelectron spectroscopy （PES） measurements and first-principles calculations. The PES spectrum of the entire occupied valence band is reported, which exhibits abundant spectral features from the Fermi level to - 24 eV binding energy. All the spectral features are broadened as compared with the cases of C60. The reasons for the broadening are analysed by comparing the experimental data with the calculated energy levels and density of states. Special attention is paid to the analysis of the C60 highest occupied molecular orbitM （HOMO）-1 derived states, which can play a crucial role in the bonding at the interfaces of PCBM/polymer blenders or PCBM/electrodes. Besides the well-known energy level splitting of the C60 backbone caused by the lowered symmetry, C 2p states from the side chain mix or hybridize with the molecular orbitals of parent C60. The contribution of the O 2p states can substantially modify the PES spectrum.展开更多
We investigate the electronic states of IC_(60)BA and PC_(71)BM using first-principles calculations and photoelectron spectroscopy(PES)measurements.The energy level structures for all possible isomers are reported and...We investigate the electronic states of IC_(60)BA and PC_(71)BM using first-principles calculations and photoelectron spectroscopy(PES)measurements.The energy level structures for all possible isomers are reported and compared with those of C_(60),C_(70) and PC61BM.The attachment of the side chains can raise the LUMO energies and decrease the HOMO-LUMO gaps,and thus helps to increase the power-conversion efficiency of bulk heterojunction solar cells.In the PES studies,we prepared IC_(60)BA and PC_(71)BM films on Si:H(111)substrates to construct adsorbate/substrate interfaces describable with the integer charge-transfer(ICT)model.Successful measurements then revealed that one of the most important material properties for an electron acceptor,the energy of the negative integer charge-transfer state(E_(ICT)-),is 4.31 eV below the vacuum level for PC_(71)BM.The E_(ICT)- of IC_(60)BA is smaller than 4.14 eV.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11079028)the National SynchrotronRadiation Laboratory of China
文摘We have studied the electronic structure of [6,6]-phenyl-C61-butyric-acid-methyl-ester （PCBM） using synchrotron radiation photoelectron spectroscopy （PES） measurements and first-principles calculations. The PES spectrum of the entire occupied valence band is reported, which exhibits abundant spectral features from the Fermi level to - 24 eV binding energy. All the spectral features are broadened as compared with the cases of C60. The reasons for the broadening are analysed by comparing the experimental data with the calculated energy levels and density of states. Special attention is paid to the analysis of the C60 highest occupied molecular orbitM （HOMO）-1 derived states, which can play a crucial role in the bonding at the interfaces of PCBM/polymer blenders or PCBM/electrodes. Besides the well-known energy level splitting of the C60 backbone caused by the lowered symmetry, C 2p states from the side chain mix or hybridize with the molecular orbitals of parent C60. The contribution of the O 2p states can substantially modify the PES spectrum.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11079028 and 11374258。
文摘We investigate the electronic states of IC_(60)BA and PC_(71)BM using first-principles calculations and photoelectron spectroscopy(PES)measurements.The energy level structures for all possible isomers are reported and compared with those of C_(60),C_(70) and PC61BM.The attachment of the side chains can raise the LUMO energies and decrease the HOMO-LUMO gaps,and thus helps to increase the power-conversion efficiency of bulk heterojunction solar cells.In the PES studies,we prepared IC_(60)BA and PC_(71)BM films on Si:H(111)substrates to construct adsorbate/substrate interfaces describable with the integer charge-transfer(ICT)model.Successful measurements then revealed that one of the most important material properties for an electron acceptor,the energy of the negative integer charge-transfer state(E_(ICT)-),is 4.31 eV below the vacuum level for PC_(71)BM.The E_(ICT)- of IC_(60)BA is smaller than 4.14 eV.
