The Effect of Controlled Dopant Concentration on the Performance of Blue Polymer Light‐emitting Diodes |
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| Authors: | Ping‐Tsung Huang Cheng‐Wei Chou Mei‐Ying Chang Wen‐Yao Huang Chih‐Chien Lee Yu‐Kai Han Shun‐Wei Liu |
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| Institution: | 1. Department of Chemistry, Fu Jen Catholic University, Taipei 24205, Taiwan, R.O.C.;2. Department of Photonics and Institute of Electro‐Optical Engineering, National Sun Yat‐Sen University, Kaohsiung 804, Taiwan, R.O.C.;3. Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, R.O.C.;4. Department of Chemical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan, R.O.C.;5. Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan, R.O.C. |
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| Abstract: | The performance of a blue polymer light‐emitting diodes (PLED) was significantly improved by doping a controlled amount (<1%) of a hole transport molecule N,N′‐bis‐(1‐naphthyl)‐N,N′‐diphenyl‐1,1′‐biphenyl‐4,4″‐diamine (NPB) into the emitting layer. Hole carrier mobility of the blue emitting polymer, BP105 (trade name of The Dow Chemicals Co.), increased from 5.27 × 10‐7 cm‐2/Vs of the pristine BP105 to 1.80 × 10‐6 cm‐2/Vs with the addition of 1% NPB in BP105. The enhanced carrier mobility greatly promoted performance of a blue PLED device with a device structure of ITO/PEDOT:PSS/BP105+x% NPB/LiF/Ca/Al. Luminance increased from 573 cd/m2 to 2,720 cd/m2 at 6V and efficiency increased from 1.1 lm/W to 1.6 lm/W at 1,000 cd/m2 with 1% NPB in BP105. The most important improvement was an increase in the lifetime of the blue device from 80 to 120 hours at an initial luminance of 400 cd/m2. We found that by choosing the appropriate dopant with good energy alignment and controlled dopant concentration, the performance of a blue PLED device could be greatly improved. |
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| Keywords: | PLED NPB Mobility Lifetime |
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