Introduction
< Key Points >
Using the JASCO CPL-300 circularly polarized luminescence measurement system and a dedicated accessory, the circularly polarized electroluminescence (CPEL) spectrum of circularly polarized organic light emitting diodes (CP-OLEDs) can be measured.
A CP-OLED emits circularly polarized luminescence (CPL) under an applied voltage, and has potential applications in devices such as 3D displays and lights for plant growth.1) In this study, evaluation of the properties of CP-OLEDs is preformed using a CPL measurement system with a dedicated accessory that allows easy alignment of the optical axis of the device and simple electrode wiring, so that stable measurements can be performed (Figure 1). In this report, we describe the use of this accessory to evaluate the CPEL properties of a CP-OLED device with fac-Λ-Ir(ppy)3 as an emitting layer.
Fig. 1 External view of CP-OLED accessory
Experimental
Sample
CP-OLED device with fac-Λ-Ir(ppy)3 (Figure 2) as emitting layer
(Light-emitting area: 2 mm x 2 mm)
Fig. 2 Structure of fac-Λ-Ir(ppy)3
System
Instrument: CPL-300 CPL measurement system
Accessory: Dedicated CP-OLED accessory*
Software: Spectra measurement program
* This product is a custom-ordered item.
Parameters
Em. bandwidth： 10 nm
Scanning speed: 100 nm/min
Response: 4 s
Data interval： 0.5 nm
Accumulations: 2
Measurement procedure
Figure 3 shows the measurement procedure using the dedicated CP-OLED accessory.
Fig. 3 Measurement procedure
Keywords
CPEL, CP-OLED, CPL, Circularly polarized electroluminescence, Circularly polarized organic light emitting diode, Circularly polarized luminescence, Device
Results
Figure 4 shows a photograph of the CP-OLED device under an applied voltage of 11 V. The device is seen to exhibit strong green light emission. The corresponding CPEL and EL spectra are shown in Figure 5. The EL spectrum has a peak wavelength of 514 nm and a positive CPEL signal is produced.
Fig. 4 Photograph of the light-emitting surface
Fig. 5 CPEL and EL spectra
Conclusion
The CPEL and EL spectra of a CP-OLED device with fac-Λ-Ir(ppy)3 as the emitting layer and an emission area of 2 x 2 mm were measured using a dedicated CP-OLED accessory. This accessory allows easy alignment of the optical axis of the device and simplifies electrode wiring, so that stable CPEL measurements can be performed.
References
1.D.-W. Zhang, M. Li, C.-F. Chen: Chem. Soc. Rev., 49, 1331 (2020). DOI: 10.1039/C9CS00680J
Acknowledgements
This work was performed under the guidance of Prof. Yoshitane Imai, Faculty of Science and Engineering, Kindai University.
