Organic light-emitting diodes based on sodium chloride buffer layer
Abstract
Since the organic light-emitting diodes (OLEDs) have broad application prospects in the field of display and lighting due to low drive voltage, high brightness and current efficiency, fast response time, easy to realize large area flexible and other advantages, etc. However, the high price of this diode seriously affected the pace of its market. In this paper, the sodium chloride (NaCl) film was used as a cathode buffer layer of OLED device. The device structure is ITO/NPB (60 nm)/Alq<sub>3</sub> (50 nm)/NaCl (<italic>x</italic> nm)/Al (100 nm) devices, including <italic>x</italic>=0, 1.5, 2, 2.5, 3, 3.5 nm. The influence of the thickness of NaCl film on the performance of OLED was studied by analyzing the voltage and current characteristics of the device. When a layer of NaCl film was inserted between the cathode and the Alq<sub>3</sub>, the <italic>J</italic>-<italic>V</italic> characteristic curve of the device was obviously shifted to the left, and the turn-on voltage of the device decreased obviously. Moreover, with the increase of the thickness of the NaCl film, the turn-on voltage of the device decreased with the increase of the thickness (0–2 nm) film. When the thickness of the NaCl film is 2 nm, the voltage of the device was the lowest. If the thickness of NaCl film was more than 2.5 nm, the turn-on voltage of the device increased slowly with the increase of the thickness of the NaCl film. However, even if the thickness of the NaCl film increased to 3.5 nm, the turn-on voltage of the device was much lower than that of the NaCl thin film device. When the thickness of the NaCl film is less than 2.5 nm, the current efficiency of the device is much larger than that of the device without NaCl film. At the same time, the physical mechanism was analyzed by combining the tunneling equation. This study gives a new way to reduce the cost of OLED production.
