“…We used fi ve types of electron-transporting materials (ETMs) for the ETL: tris(8-quinolinolato)aluminum (Alq 3 ), 1,4-di(1,10-phenanthrolin-3-yl)benzene (DPB), bis-1,2-(3,5-di-3-pyridylphenyl) benzene (B3PyPB), [ 11 ] bis-4,6-(3,5-di-3-pyridyl-phenyl)-2-methylpyrimidine (B3PyMPm), [ 12 , 13 ] and bis-4,6-(3,5-di-4-pyridyl-phenyl)-2-methylpyrimidine (B4PyMPm). [ 13 ] Two hole-transporting materials (HTMs), N , N ′ -di(naphthalene-1-yl)-N , N ′ -diphenylbenzidine (NPD) and 1,1-bis-(4-bis(4-tolyl)-aminophenyl)cyclohexene (TAPC), were used in the HTL. The ETMs are particularly important because their lowest unoccupied molecular orbital (LUMO) levels are generally not estimated from direct measurements, except inversephotoemission spectroscopy (IPES) measurements, and these values are still ambiguous.…”