氯化钠作为阴极缓冲层的有机电致发光器件

Organic light-emitting diodes based on sodium chloride buffer layer

有机发光二极管(Organic Light-Emitting Diodes,OLED)具有驱动电压低、亮度和电流效率高、响应时间快、易实现大面积柔性等突出优点,在显示和照明等领域有广阔的应用前景.但是,由于这种二极管价格高昂,严重影响了其市场化的步伐.本研究使用价格便宜的氯化钠(NaCl)薄膜作为OLED器件的阴极缓冲层,以ITO玻璃为衬底,制作了结构为ITO/NPB(60?nm)/Alq3(50?nm)/NaCl(xnm)/Al(100?nm)的器件,其中x=0,1.5,2.0,2.5,3.0,3.5?nm.通过分析器件亮度-电压-电流特性,详细研究了NaCl薄膜厚度变化对OLED性能的影响.在器件阴极和Alq3之间加入一层NaCl薄膜后,J-V特性曲线明显向左移动,器件的开启电压明显下降.并且,随着NaCl薄膜的厚度逐渐增加,在0–2.0?nm范围,器件的开启电压随着厚度的增加而明显降低.当NaCl薄膜的厚度为2.0?nm时,器件的开启电压最低.NaCl薄膜的厚度超过2.5?nm时,随着NaCl薄膜厚度的增加,器件的开启电压也缓慢增加.但是,即使NaCl薄膜的厚度增加到3.5?nm,器件的开启电压还是远低于没有插入NaCl薄膜器件的开启电压.当插入NaCl薄膜的厚度小于2.5?nm时,器件的电流效率远大于没有NaCl薄膜的器件.同时,结合载流子隧穿方程,深入分析了相关的物理机制.本研究为降低OLED生产成本开辟了一条新的途径.

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）/Alq3 （50 nm）/NaCl （x nm）/Al （100 nm） devices, including x=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 Alq3, the J-V 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.