Electron Transport Characteristics in Bepp2:Liq Thin Film and Its Influence on Electroluminescent Device Performance

摘要

The electron transport properties in bis[2-(2-hydroxyphenyl)-pyridine] beryllium (Bepp(2)) doped 8-hydroxyquinolinolatolithium (Liq) are investigated by impedance spectroscopy (IS). The Nyquist curves indicate that the electron-only device based on Bepp(2):Liq displays much larger bulk resistance R-p than the Bepp(2):Li2CO3 device, which has a great impact on electron transport ability. The electron mobility of Bepp(2):Liq film (10(-6)similar to 10(-5) cm(2) V-1 s(-1)) is 1 to 2 orders of magnitude lower than that of the Bepp(2):Li2CO3 film (similar to 10(-4) cm(2) V(-1 )s(-1)) It is slightly higher than the electron mobility of the pure Bepp(2) film even though they have the same order of magnitude at the low electric field region. It is found that the electron mobility in Bepp(2):Liq film increases as the electric field is increased. The performance of green organic light-emitting diode (OLED) with Bepp(2):Liq as an electron transport layer (ETL) is a little lower than that of the device using Bepp(2):Li2CO3 as ETL and much higher than that of the Bepp(2 )ETL device. The reasons for the differences of device performance have been explored through analyzing the electron injection and transport.

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