Unusual Optical, Electric, and Magnetic Behaviors of OLEDs due to Exothermic/Endothermic Dexter-Energy-Transfer and Fusion Channels of Hot/Cold Triplet ExcitonsClick to copy article linkArticle link copied!
- Yuting WuYuting WuChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Yuting Wu
- Jingjing WangJingjing WangChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Jingjing Wang
- Jing ChenJing ChenChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Jing Chen
- Huiyao WangHuiyao WangChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Huiyao Wang
- Song YangSong YangSchool of Science, Guizhou University of Engineering Science, Bijie 551700, ChinaMore by Song Yang
- Hong LuHong LuSchool of Science, Guizhou University of Engineering Science, Bijie 551700, ChinaMore by Hong Lu
- Junhong LiuJunhong LiuChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Junhong Liu
- Bo WangBo WangChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Bo Wang
- Teng PengTeng PengChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Teng Peng
- Jun YangJun YangChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Jun Yang
- Yingqiong ZhouYingqiong ZhouChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Yingqiong Zhou
- Keyi ZhangKeyi ZhangChongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Keyi Zhang
- Zuo LiZuo LiSchool of Science, Guizhou University of Engineering Science, Bijie 551700, ChinaMore by Zuo Li
- Yingfei YiYingfei YiSchool of Science, Guizhou University of Engineering Science, Bijie 551700, ChinaMore by Yingfei Yi
- Lihong ChengLihong ChengSchool of Science, Guizhou University of Engineering Science, Bijie 551700, ChinaMore by Lihong Cheng
- Sijie Zhang*Sijie Zhang*Email: [email protected]School of Science, Guizhou University of Engineering Science, Bijie 551700, ChinaCollege of Physics, Sichuan University, Chengdu 610065, ChinaMore by Sijie Zhang
- Tian Yu
- Hongqiang ZhuHongqiang ZhuChongqing Key Laboratory of Photo-Electric Functional Materials, Chongqing Normal University, Chongqing 401331, ChinaMore by Hongqiang Zhu
- Zuhong Xiong*Zuhong Xiong*Email: [email protected]Chongqing Key Laboratory of Micro&Nano Structure Optoelectronics, School of Physical Science and Technology, Southwest University, Chongqing 400715, ChinaMore by Zuhong Xiong
Abstract
Hot-exciton-based organic light-emitting diodes (HE-OLEDs) have aroused more attention due to their advantages of low cost, high efficiency, and negligible efficiency roll-off. However, their physical behaviors need further investigation because of the evolution diversity of excited states existing in HE-OLEDs. Herein, we employ the two frequently used hosts tris(8-hydroxyquinoline)aluminum (Alq3) and 4,4′-N,N′-dicarbazolebiphenyl (CBP) and the hot-exciton emissive guests rubrene (Rb) and its derivative 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb) to make four HE-OLEDs and use well-known fingerprint magneto-electroluminescence (MEL) curves to probe their microscopic dynamic processes. Interestingly, we find abundant optical, electric, and magnetic behaviors of HE-OLEDs due to exothermic and endothermic Dexter-energy-transfer (DET) and triplet fusion (TF) channels of hot/cold excitons. Specifically, for the case of different bias currents at room temperature, both the low-field MEL curves of Rb- and TBRb-doped Alq3-based OLEDs show a normal intersystem crossing (ISC) of polaron pairs, but those of Rb- and TBRb-doped CBP-based OLEDs present a conversion from a high-level reverse ISC (HL-RISC, S1 ← T2) to an ISC and a normal HL-RISC, respectively, which weakens with an elevated bias current. Moreover, both the high-field MEL curves of Rb- and TBRb-doped Alq3-based (CBP-based) OLEDs show a normal T1F (T2F) of cold (hot) triplet excitons, which strengthens with elevated bias currents. For the case of constant bias currents at variable temperatures, both the low-field MEL curves of Rb- and TBRb-doped Alq3-based OLEDs show an abnormal ISC, which rises with a reducing temperature, but those of Rb- and TBRb-doped CBP-based OLEDs depict a conversion from an ISC to a HL-RISC and a normal HL-RISC, respectively, which intensifies with a decreasing temperature. In addition, the high-field MEL curves of Rb- and TBRb-doped Alq3-based OLEDs separately show a normal and an abnormal T1F, but those of both of Rb- and TBRb-doped CBP-based OLEDs exhibit a normal T2F, which strengthens with a reducing temperature. Furthermore, the quantum efficiency of Rb- and TBRb-doped Alq3-based OLEDs separately show nonmonotonically and monotonically decreased tendencies, but both Rb- and TBRb-doped CBP-based OLEDs show monotonically increased tendencies with a decreasing temperature. Surprisingly, all of the above enriched physical behaviors can be reasonably interpreted within the frames of excited state dynamics that DET from host cold T1,Alq3 (T1,CBP) to guest hot T2 is an endothermic (exothermic) process and T1F in Rb (TBRb) is an exothermic (endothermic) process, but T2F in both Rb and TBRb is exothermic.
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