Organic Light-emitting Diodes Based On Photovoltaic-type Charge Generation Layer Of C₆₀/CuPc

In recent years, organic light-emitting devices（OLEDs） have attracted remarkable attention because of the appealing commercial interest for flat panel display, next generation indoor lighting source and flexible displays. In the past decades, OLED entered into the commercial market from the stage of experimental research gradually. In order to improve the performance of OLED, this paper combined the photovoltaic-type charge generation layer（CGL） with different OLED, such as tandem OLED, tandem WOLED and single emitting unit OLED. As a result, the current efficiency and brightness of OLEDs are improved. The main research contents include three parts as follow:1. The bilayer film of C₆₀/CuPc was used as photovoltaic-type CGL in red tandem OLED to improve current efficiency; meanwhile remained a low driving voltage. First, we used Ir（piq）2acac as the main emitter to fabricate tandem OLED with the structure of Li F/C₆₀/CuPc/MoO3 as the CGL. The optimized structure was Li F（1 nm）/C₆₀（5 nm）/CuPc（5 nm）/MoO3（3 nm） by adjusting the thickness of C₆₀ and CuPc. The current efficiency of tandem OLED improved 2.1 times, while the voltage increased in less than two times compared to single OLED. Second, this study proved further the function of photovoltaic-type CGL C₆₀/CuPc by fabricating the green tandem OLED with the same CGL and comparing the performance of red tandem OLED with bulk heterojunction CGL of C₆₀:CuPc.2. The photovoltaic-type CGL of C₆₀/CuPc was used in tandem WOLED. First, we changed the relative position between blue emitting layer of FIrpic and red emitting layer of Ir（piq）2acac to achieve tandem WOLED and then researched the optical and electrical performance. Besides, the orange fluorescent material of DCJTB was used to fabricate tandem WOLED and got the better performance. Second, we compared the performance of tandem WOLEDs with traditional CGL（Ag） and photovoltaic-type CGL(C₆₀/CuPc), then demonstrated the key role of C₆₀/CuPc in tandem WOLED.3. The photovoltaic-type CGL of C₆₀/CuPc was used in single emitting unit OLED. First, we fabricated the red, green and blue OLED with Ir（piq）2acac, Ir（ppy）3 and FIrpic as the emitter, respectively; and studied the influence on device performance with different position and different type of CGL. Second, we got the optimal thickness of CGL was C₆₀（5 nm）/CuPc（15 nm） and optimal position was between Bphen and cathode. Finally, the current efficiency and brightness of single OLED improved significantly compared with standard OLED, which can comfirm the properties of photovoltaic-type CGL further.