[Properties of phosphorescent organic light-emitting diodes with different doping order on light emitting layer]

Utilizing GIr1(green) and R-4B(red) phosphorescent dye, organic light-emitting diodes with different doping orders on red and green light-emitting layers were fabricated. The authors investigated the luminescent properties of devices combined with the effect of electron (TCTA) and hole (BCP) blocking layer. The results showed that the great impacts on spectrum, light efficiency, luminance and luminescent color were produced based on different doping order, and the authros also found the strong emission peak at the interface of the BCP and CBP layer. With the use of the red and green doping type, 0.527 mA x cm(-2), 104 cd x m(-2), 19.75 cd x A(-1) and (0.371 7, 0.576 8) could be reached, respectively. The reasons were that on the one hand, because of large difference between energy levels of host material CBP and doping material GIr1, R-4B, and charge trapping and hopping via dopants were the main mechanism of change; on the other hand, for the different energy levels between dopants and blocking layers, the doping sequence could affect barrier distribution, and then affect the electric field distribution.