|
|
|
|
|
|
| Highly Efficient Solution Processed Blue Thermally Activated Delayed Fluorescent Organic Light-Emitting Devices with a Mixed Hole Injection Layer |
| YANG Jian1, 2, ZHAO Su-ling1, 2*, SONG Dan-dan1, 2, XU Zheng1, 2, QIAO Bo1, 2, WANG Peng1, 2, WEI Peng1, 2 |
1. Key Laboratory of Luminescence and Optical Information, Institute of Optoelectronic Technology, Beijing 100044, China
2. Beijing Jiaotong University, Beijing 100044, China |
|
|
|
|
Abstract In the study of the solution-processed organic light-emitting devices (OLEDs), PEDOT∶PSS is often used as a hole injection layer (HIL) in OLEDs due to its good film-forming property and high light transmittance. However, related studies have shown that PEDOT∶PSS itself has defects, such as poor stability and low work function, which may result in poor and unstable device performance. At the same time, blue light is one of the three primary colors of the display, and the preparation of high efficient blue light OLEDs is indispensable for realizing high-quality white light and solid-state lighting devices. At present, most solution-processed blue OLEDs suffer from poor device performance, hence the research on the highly efficient solution-processedblue OLEDs will be of great significance. In this paper, we applied an efficient blue thermally activated delayed fluorescent (TADF) emitter DMAC-DPS to fabricate solution-processed blue TADF OLEDs，and the mixed hole injection layers (mix-HILs) were prepared by doping PEDOT∶PSS with PSS-Naand its effect on device performance of blue-light TADF OLEDs was investigated. First, we mixed different volumes of PSS-Na solution in PEDOT∶PSS aqueous solution and the mix-HILs were spin-casted under the same conditions to fabricate blue OLEDs. The electroluminescence (EL) spectrum is blue-shifted after the incorporation of PSS-Na, which can be attributed to the decrease in the thickness of the mix-HIL layer. The reduction in the thickness of the mix-HIL layer results in a blue shift in the EL spectrum under the effect of the microcavity. By comparing the current density-voltage-luminance (J-V-L) curves and its calculated current efficiency of each device, the results show that with the incorporation of PSS-Na, the brightness and current of the device increase, and the current efficiency of the device is also improved. The increase is the highest when the doping ratio is 0.5∶0.5 (PEDOT∶PSS/PSS-Na) of which the device brightness is increased by 86.7% and the current efficiency is increased by 34.3%. Finally, the behavior of internal carriers of blue OLEDs based on mix HILs with different doping ratios was observed by means of transient electroluminescence (EL) test system. Forward bias of 10 V was applied to the blue OLEDs. When the electroluminescence of the device reached a steady-state, the bias was removed, and the intensity of the delayed EL peak was observed. After a time delay of 50 μs, a reverse bias of 7 V was applied to observe the intensity of transient EL peak. It shows that after the removal of the forward bias, the EL spike of the device decreases as the PSS-Na incorporation ratio increases, indicating that the accumulated charge at the internal interface of the device is reduced. And the increase in the EL spike of the device after application of the reverse bias indicates that the injection of holes is more efficient after the incorporation of PSS-Na, and the injection barrier at the mix-HIL/EML interface is decreased. With the help of transient EL test system, the change of EL intensity of the device was observed by applying or removing the driving voltage, and the charge accumulation at the mix-HIL/light-emitting layer (mix-HIL/EML) interface was analyzed. The incorporation of PSS-Na increases the work function of the hole injection layer, and the accumulation of charge at the interface is reduced. By preparing the mix-HIL with doping PSS-Na into PEOT∶PSS, the device performance of blue TADF OLEDs is improved, which is a feasible method for obtaining high efficient solution-processed OLEDs.
|
|
Received: 2019-04-09
Accepted: 2019-08-06
|
|
|
|
Corresponding Authors:
ZHAO Su-ling
E-mail: slzhao@bjtu.edu.cn
|
|
[1] McCarthy M A, Liu B, Donoghue E P, et al. Science, 2011, 332：570.
[2] Baldo M A, O’Brien D F, You Y, et al. Nature, 1998, 395：151.
[3] Kondakov D Y, Pawlik T D, Hatwar T K, et al. Journal of Applied Physics, 2009, 106: 124510.
[4] Li W, Liu D, Shen F, et al. Advanced Functional Materials, 2012, 22：2797.
[5] Endo A, Ogasawara M, Takahashi A, et al. Advanced Materials, 2009, 21：4802.
[6] Uoyama H, Goushi K, Shizu K, et al. Nature, 2012, 492：234.
[7] Lin T A, Chatterjee T, Tsai W L, et al. Advanced Materials, 2016, 28：6976.
[8] Cho Y J, Chin B D, Jeon S K, et al. Advanced Functional Materials, 2015, 25：6786.
[9] Luo J, Gong S, Gu Y, et al. Journal of Materials Chemistry C, 2016, 4：2442.
[10] Duan L, Hou L, Lee T W, et al. Journal of Materials Chemistry, 2010, 20：6392.
[11] Ma H, Yip H L, Huang F, et al. Advanced Functional Materials, 2010, 20：1371.
[12] Pu Y J, Chiba T, Aizawa N, et al. Journal of Photopolymer Science and Technology, 2013, 26：403.
[13] Kim Y H, Wolf C, Cho H, et al. Advanced Materials, 2016, 28：734.
[14] Alemu D, Wei H Y, Ho K C, et al. Energy & Environmental Science, 2012, 5：9662.
[15] Chen Y, Hao L, Zhang X, et al. Journal of Applied Physics, 2017, 122: 065304.
[16] Zhang C, Qiao B, Zhao S, et al. Organic Electronics, 2016, 39：348.
[17] Zuo C, Ding L. Advanced Energy Materials, 2017, 7: 1601193.
[18] Lee S S, Ko D, Chung C H, et al. Synthetic Metals, 2002, 128：51.
[19] YANG Zhao-kun, ZHAO Su-ling, XU Zheng, et al(杨照坤，赵谡玲，徐 征，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2016, 36（10）, 3134.
[20] Wei P, Zhang D, Cai M, et al. Organic Electronics, 2017, 49：242. |
| [1] |
YANG Chao-pu1, 2, FANG Wen-qing3*, WU Qing-feng3, LI Chun1, LI Xiao-long1. Study on Changes of Blue Light Hazard and Circadian Effect of AMOLED With Age Based on Spectral Analysis[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(01): 36-43. |
| [2] |
CUI Can1,2, SONG Dan-dan1,2, ZHAO Su-ling1,2, QIAO Bo1,2, XU Zheng1,2*. Improving the Efficiency of Solution-Processed, Blue Fluorescent Organic Light-Emitting Diodes (OLEDs) by Employing TADF Exciplex Hosts[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(03): 700-705. |
| [3] |
YANG Lei1, 2, LI Ang1*, XIE Pin-hua1, 2, HU Zhao-kun1, 2, LIANG Shuai-xi1, 2, ZHANG Ying-hua1, 2, HUANG Ye-yuan1, 2. Telemetry Research of NO2 Concentration in the Night Based on LED and DOAS Method[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(05): 1398-1405. |
| [4] |
WANG Hao1, 2, ZHAO Su-ling1, 2*, XU Zheng1, 2, SONG Dan-dan1, 2, QIAO Bo1, 2, WANG Peng1, 2, ZHENG Wei-ye1, 2, WEI Peng1, 2. The Influence of Deep Trap on the Efficiency Decrease in PhOLEDs Based on Double Dopants Strategy[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(04): 1018-1024. |
| [5] |
YANG Chao-pu1,2, FANG Wen-qing3*, LIU Ming-bao1,2, LI Chun1,2, ZHANG Mei-li1,2, HAN Xi1,2, LIU Yan-feng1,2, DAI Wei-li1,2. A Visualization Evaluation Method for Blue Light Hazard and Circadian Effect of Light Source[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2018, 38(11): 3476-3482. |
| [6] |
HONG Xiao-xia1, 2, XU Zheng1, 2*, ZHAO Su-ling1, 2, QIAO Bo1, 2, ZHANG Cheng-wen1, 2, WANG Peng1, 2 . Study on the Overshoot Effect of Doped PhOLED with Transient Electroluminescence[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2017, 37(03): 710-714. |
| [7] |
YANG Zhao-kun, ZHAO Su-ling*, XU Zheng*, HUANG Qing-yu . The Inside Charge Behavior of Organic Light-Emitting Diodes Investigated with Transient Electroluminescent Measurements[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2016, 36(10): 3134-3137. |
| [8] |
LI Rui-qin, QIU Jian-bei, YANG Zheng-wen*, LIAO Jia-yan, WU Hang-jun, LAI Shen-feng, SONG Zhi-guo, YANG Yong, ZHOU Da-cheng, WANG Rong-fei . Preparation and Up-Conversion Luminescence Properties of Yb3+/Tm3+ Co-Doped Sb2O4 Powder [J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2014, 34(03): 630-633. |
| [9] |
SHEN Chong-yu, XU Zheng*, ZHAO Su-ling, HUANG Qing-yu . Study on the Safety of Blue Light Leak of LED [J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2014, 34(02): 316-321. |
| [10] |
DAI Shuang, YU Tong-jun*, LI Xing-bin, YUAN Gang-cheng, LU Hui-min . The Electroluminescence Spectra of InGaN/GaN Blue LEDs During Aging Time [J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2014, 34(02): 327-330. |
| [11] |
XI Jian-fei1，2，ZHANG Fang-hui1，2，MU Qiang1，ZHANG Mai-li1，2 . The Spectrogram Characteristics of Organic Blue-Emissive Light-Emitting Excitated YAG∶Ce Phosphor [J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2011, 31(09): 2337-2340. |
| [12] |
SONG Guo-li1，FANG Xiang-yun2，LIANG Hong1 . Effect of O2/Ar Ratio on Blue Photoluminescence Spectrum of Nanocrystalline ZnO Films[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2010, 30(03): 591-594. |
| [13] |
CHEN Liu-qing1, 2,LIU Xu-guang2, 3*, XU Hui-xia1, 2, WANG Hua1, 2, XU Bing-she1, 2 . Characterization and Photoluminescence Properties of a Blue-Light-Emitting Material[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2009, 29(05): 1201-1204. |
| [14] |
LI Fang1, ZHENG Huai-li2. Study on Fenton-Methylene Blue Spectral Analysis Method for Determining the Inhibitory Effect of Quercetin Complexes on Hydroxyl Free Radical[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2006, 26(12): 2294-2297. |
|
|
|
|
