Development of 10V AC drive surface luminous red LED element in Japan

Japan's Industrial Technology Research Institute has developed a surface emitting red LED element with an AC voltage of about 10V. Production research, said its luminous voltage in the previous LED components below 1/10. The realization of the red EL element on the low voltage drive surface not only reduces the volume of the power supply, but also has a wide viewing angle. In the future, with the development of high brightness and multi color, is expected to be used for lighting appliances, light sources and displays, etc..

The development of the LED element of each layer of materials using perovskite (Perovskite) oxide. The chemical properties of the material are stable, and the characteristics of oxidation and heating are almost unchanged. Therefore, the packaging process and the manufacturing process can be shortened. Prior to this, the study found that the majority of perovskite type oxides due to ultraviolet radiation can emit significant fluorescence, so it was made of light-emitting film. This time, the perovskite type oxide and insulator film lamination, trying to develop a good stability of LED components.

The newly developed LED element uses the pulsed laser deposition (PLD) method to make the insulating layer, the luminescent layer and the insulating layer on the electrode bottom plate. ArF excimer laser (wavelength 193NM). Production conditions for the bottom temperature of 700 degrees, the environment is 10PA oxygen. After heat treatment in the atmosphere, the transparent electrode is made of LED element by PLD method.

The material of the electrode bottom plate, the luminous layer and the insulating layer are as follows. All of the materials are less resource constrained. Firstly, the electrode bottom plate is made of strontium titanate (1%Nb-SrTiO3) with 1% niobium (Nb). In the A part of perovskite type oxide (ABO3) strontium calcium titanate (Ca0.6Sr0.4) TiO3, the luminescent layer is added with a small amount of praseodymium (Pr) as the luminescent center. Perovskite type oxide strontium titanate (SrTiO3) was used in the insulating layer. Using the PLD law to make these films grow continuously, and form the structure of the 2 layers of insulating layer to hold the light emitting layer, a double insulation structure thin film EL element has been developed". The transparent electrode above is ITO (indium tin oxide) or SnO2 film.

Firstly, a EL element with a single layer of light-emitting layer is formed. When the AC voltage is applied to 14V and 1KHz, the red surface of the transparent electrode is red. The luminescence spectrum shows a sharp peak of 612nm. This is believed to be caused by the energy transfer from the Pr3+ to the 3H4 1D2, starting with a voltage of about 10V. And when the double layer light emitting layer element is produced, a strong red surface luminescence can be obtained by using the 24V voltage of about 2 times the LED component of the single layer light-emitting layer.

In addition, the results of this study will be published in the German scientific journal Advanced Materials.

Fig. 1 the luminescence of the LED element using the perovskite type oxide

Figure 2 the development of the LED component model

Fig. 3 the luminescence spectrum of the LED element and the photo of the light emitting element: the double insulation structure of the single layer EL (left), the double insulation layer EL (right)

Figure 4 Comparison of the characteristics of various EL components