Low driving voltage white organic light-emitting diodes with high efficiency and low efficiency roll-off
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- 作者：Zhensong Zhang ; Pingrui Yan ; Shouzhen Yue ; Yu Chen ; Qingyang Wu ; Dalong Qu ; Runda Guo ; Peng Wang ; Yi Zhao ; Shiyong Liu
- 关键词：White light ; High efficiency ; Low operating voltage ; Low efficiency roll-off ; Charge carrier balance
- 刊名：Organic Electronics
- 出版年：2013
- 出版时间：September, 2013
- 年：2013
- 卷：14
- 期：9
- 页码：2172-2176
- 全文大小：942 K
文摘
Single emission layer white organic light-emitting diodes (WOLEDs) showing high color stability, low turn-on voltage, high efficiency and low efficiency roll-off by incorporating iridium(III) bis[(4,6-difluo-rophenyl)-pyridinato-N,C2] (FIrpic) and bis(2-phenylbenzothiazolato) (acetylacetonate)iridium(III) (Ir(BT)2(acac)) phosphors dyes have been demonstrated. Our WOLEDs without any out-coupling schemes as well as n-doping strategies show low operating voltages, low turn-on voltage (defined for voltage to obtain a luminance of 1 cd/m2) of 2.35 V, 79.2 cd/m2 at 2.6 V, 940.5 cd/m2 at 3.0 V and 10 300 cd/m2 at 4.0 V, respectively, and achieve a current efficiency of 40.5 cd/A, a power efficiency of 42.6 lm/W at a practical brightness of 1000 cd/m2, and a low efficiency roll-off 14.7 % calculated from the maximum efficiency value to that of 5000 cd/m2. Such improved properties are attributed to phosphors assisted carriers transport for achieving charge carrier balance in the single light-emitting layer (EML). Meanwhile the host-guest energy transfer and direct exciton formation process are two parallel pathways serve to channel the overall excitons to dopants, greatly reduced the unfavorable energy losses.