Efficient carrier- and exciton-confining device structure that enhances blue PhOLED efficiency and reduces efficiency roll-off

摘要

In this study we used a known host material diphenylbis[4-(9-carbazoyl)phenyljsilane (SiCa) to realize a highly efficient bis[4,6-(difluorophenyl)-pyridinato-N,C～2]picolinate (Flr pic)-based blue phosphorescent device exhibiting high efficiencies of up to 18.3%, 41.5 cd/ A, and 31 lm/W in a carrier- and exciton-confined device structure. At a practical bright ness of 1000 cd/m～2, the device performance (η_ext) remained as high as 16.7%. The enhanced efficiency and reduced roll-off resulted mainly from the introduction of (a) DTAF as an HTL that efficiently blocked and confined excitons within the FIrpic-doped emissive layer, and (b) a thin layer of DPPS between the EML and TAZ, serving as an exciton- and hole-blocking layer to suppress exciton quenching by FIrpic at the EML-ETL interface. In addition, we incorporated a red phosphorescent dopant (Mpq_2Iracac) into the blue device to fabricate a white phosphorescent organic light-emitting device, which exhibited satisfactory effi ciencies (11.6%, 21.2 cd/A, 14.2 lm/W) with the Commission Internationale de L'eclairage (CIE) coordinates of (0.35, 0.38).