High-efficiency bipolar electroluminescent polymer containing an oxadiazole pendant group

By introducing electron-deficient 1,3,4-oxadiazole pendant units into poly(p-phenylenevinylene) as a side chain, we have achieved high-performance polymer light-emitting diodes with aluminum (Al) electrodes and a luminance efficiency of ∼ 20 cd/A. These results are attributed to the high electron affinity and the good electron transport of the oxadiazole units, which facilitate electron injection from the Al electrode, and bipolar transport in the active layer. The 'bipolar' nature of this system is strongly supported by the time-of-flight measurements, which exhibit symmetric photocurrent transients between the electrons and holes, these transients are mainly responsible for the excellent performance of this system because the help achieve charge balance in the devices.