Study on Luminescent Properties of New Magenta OLED Devices
1 Introduction
Organic thin-film electroluminescent devices have developed rapidly in the past 20 years and have reached a practical level to this day. Although the high brightness, high efficiency and long life of blue and green organic thin film electroluminescent devices (OLEDs) have been widely verified by researchers, the color purity and high efficiency of red light-emitting OLED devices are flawed and need to be further deepened. Research. From the current research, there are two ways to achieve red luminescence: (1) Doping a dye that emits red light, using a dye doping that is effective for energy transfer, by forming near the hole transport layer and the luminescent interface. The excitons are captured by the dye center to achieve luminescence. (2) Using a rare earth ion complex as a matrix or an activator. Such as J. Kido uses rare earth organics as red emitters, but the emission spectrum of rare earth ion complexes is narrow, but the performance is not stable, the film formation is poor, can not be used for vacuum evaporation, can only be used in polymers, and emits light. low efficiency. Therefore, the preparation of red OLED devices tends to dope (Dopping), dispersing red light dyes with high luminescence properties in the host material, through the effective energy from the host to the luminescent guest molecules (ie, incorporated red dye) Passed to achieve efficient, stable red light devices. In addition, the doping method is used to prepare the red OLED device because the doping method is adopted, and the incorporation of the fluorescent dye into the luminescent body greatly expands the selection range of the luminescent host material.
The dye that can emit red light is not as much as other dyes, and for small organic devices, the organic film is heated and evaporated under vacuum, requiring red dye to have a certain volatility, so many ion dyes Not very suitable. In the red light device, the first dyes used are the laser dyes DCM1 and DCM2, but their concentration quenching is very obvious, and the DCM doping ratio is small, it is difficult to accurately control in actual growth, and the luminescence is also yellowish. To this end, a lot of research has been done to improve the color purity of red light. For example, the co-doping of Rubrene with Alq and DCM increases the energy transfer between Alq and DCM, suppresses the luminescence of Alq, thereby improving the purity of red light, or finding a host with a large overlap between the emission peak and the doped DCM absorption peak. Luminescent materials to improve the purity of red light. In addition, recently, in order to improve luminous efficiency, D. F. OBrien and M. A. Baldo et al. used a heavy metal dye that efficiently emits light from a triplet state, and the external quantum efficiency of the device reached 1.3% at a luminance of 100 cd/m2. 1998, C. H. Tang et al. synthesized a high-efficiency red dye (DCJTB) based on DCM with an emission peak around 620 nm. Currently, DCJTB is being widely studied as one of the most promising red organic dyes. In the fabrication of red OLED devices, DCJTB is often incorporated as a dopant into the host luminescent material. To achieve complete energy transfer, there are generally two methods: using an auxiliary dopant as an intermediary to make energy transfer from the matrix to the luminescent object more efficient; or using a more compatible organic fluorescent dye and matrix material. In order to find a highly efficient doped red OLED device, we used DCJTB as the red dye and the green luminescent materials Alq, Gaq, Inq as the host materials, and prepared the structure as ITO/TPD/Mq (M=Al3+, Ga3+, respectively). In3+)?? A series of OLED devices of DCJTB/Mq/LiF/Al, studied the effect of energy level matching between host and guest luminescence molecules on carrier injection, confinement, exciton recombination and luminescence color purity. .
2 experiment
Photoluminescence Properties of 2.1Mq (M=Al3+, Ga3+, In3+) System DCJTB is a fused ring aromatic compound and is the most ideal dopant for the current red OLED. Its molecular formula is shown in Figure 1. Figure 2 shows the comparison of the PL emission spectra of the Mq??DCJTB (ω(DCJTB) = 0.1%) system. It can be seen from Figure 2 that when the DCJTB doping concentration is low (ω(DCJTB) = 0.l %), there is a strong launch shoulder at 520nm, and a weak launch shoulder near 550nm, which corresponds to the emission of Alq and Inq respectively. In the Gaq:DCJTB system, even if the DCJTB doping concentration is very low (ω??DCJTB=0.1%), the emission of Gaq is basically not present, which indicates that the energy transfer between Gaq??DCJTB is better than the other two. The matrix is ​​more effective.
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Organic thin-film electroluminescent devices have developed rapidly in the past 20 years and have reached a practical level to this day. Although the high brightness, high efficiency and long life of blue and green organic thin film electroluminescent devices (OLEDs) have been widely verified by researchers, the color purity and high efficiency of red light-emitting OLED devices are flawed and need to be further deepened. Research. From the current research, there are two ways to achieve red luminescence: (1) Doping a dye that emits red light, using a dye doping that is effective for energy transfer, by forming near the hole transport layer and the luminescent interface. The excitons are captured by the dye center to achieve luminescence. (2) Using a rare earth ion complex as a matrix or an activator. Such as J. Kido uses rare earth organics as red emitters, but the emission spectrum of rare earth ion complexes is narrow, but the performance is not stable, the film formation is poor, can not be used for vacuum evaporation, can only be used in polymers, and emits light. low efficiency. Therefore, the preparation of red OLED devices tends to dope (Dopping), dispersing red light dyes with high luminescence properties in the host material, through the effective energy from the host to the luminescent guest molecules (ie, incorporated red dye) Passed to achieve efficient, stable red light devices. In addition, the doping method is used to prepare the red OLED device because the doping method is adopted, and the incorporation of the fluorescent dye into the luminescent body greatly expands the selection range of the luminescent host material.
The dye that can emit red light is not as much as other dyes, and for small organic devices, the organic film is heated and evaporated under vacuum, requiring red dye to have a certain volatility, so many ion dyes Not very suitable. In the red light device, the first dyes used are the laser dyes DCM1 and DCM2, but their concentration quenching is very obvious, and the DCM doping ratio is small, it is difficult to accurately control in actual growth, and the luminescence is also yellowish. To this end, a lot of research has been done to improve the color purity of red light. For example, the co-doping of Rubrene with Alq and DCM increases the energy transfer between Alq and DCM, suppresses the luminescence of Alq, thereby improving the purity of red light, or finding a host with a large overlap between the emission peak and the doped DCM absorption peak. Luminescent materials to improve the purity of red light. In addition, recently, in order to improve luminous efficiency, D. F. OBrien and M. A. Baldo et al. used a heavy metal dye that efficiently emits light from a triplet state, and the external quantum efficiency of the device reached 1.3% at a luminance of 100 cd/m2. 1998, C. H. Tang et al. synthesized a high-efficiency red dye (DCJTB) based on DCM with an emission peak around 620 nm. Currently, DCJTB is being widely studied as one of the most promising red organic dyes. In the fabrication of red OLED devices, DCJTB is often incorporated as a dopant into the host luminescent material. To achieve complete energy transfer, there are generally two methods: using an auxiliary dopant as an intermediary to make energy transfer from the matrix to the luminescent object more efficient; or using a more compatible organic fluorescent dye and matrix material. In order to find a highly efficient doped red OLED device, we used DCJTB as the red dye and the green luminescent materials Alq, Gaq, Inq as the host materials, and prepared the structure as ITO/TPD/Mq (M=Al3+, Ga3+, respectively). In3+)?? A series of OLED devices of DCJTB/Mq/LiF/Al, studied the effect of energy level matching between host and guest luminescence molecules on carrier injection, confinement, exciton recombination and luminescence color purity. .
2 experiment
Photoluminescence Properties of 2.1Mq (M=Al3+, Ga3+, In3+) System DCJTB is a fused ring aromatic compound and is the most ideal dopant for the current red OLED. Its molecular formula is shown in Figure 1. Figure 2 shows the comparison of the PL emission spectra of the Mq??DCJTB (ω(DCJTB) = 0.1%) system. It can be seen from Figure 2 that when the DCJTB doping concentration is low (ω(DCJTB) = 0.l %), there is a strong launch shoulder at 520nm, and a weak launch shoulder near 550nm, which corresponds to the emission of Alq and Inq respectively. In the Gaq:DCJTB system, even if the DCJTB doping concentration is very low (ω??DCJTB=0.1%), the emission of Gaq is basically not present, which indicates that the energy transfer between Gaq??DCJTB is better than the other two. The matrix is ​​more effective.
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