Effect of the purity of the host material 2FPPICz on the performance of crystalline organic light-emitting diodes

The highly ordered arrangement of molecules in crystalline organic light-emitting diodes (C-OLEDs) endows C-OLEDs with high carrier mobility and photon output power. In recent years, there has been tremendous research on crystalline OLEDs. However, there has been no research on how the purity of materials affects the performance of crystalline OLED devices. In this paper, by changing the purity of the host material 2FPPICz, its influence on the current density, brightness, current efficiency, power efficiency, and other properties of crystalline OLED devices has been studied. Two C-OLED structures with different luminescent systems—organic solid-solution C-OLED devices and nanoaggregate C-OLED devices—were constructed. The results showed that where the purity of the 2FPPICz host material only affected the transport of hole carriers and did not participate in energy transfer luminescence, the higher the purity of 2FPPICz and the better the performance of the crystalline OLED device. For C-OLEDs in the energy transfer luminescence system, where the 2FPPICz host material participated in energy transfer, increasing the purity of the host material would improve the performance of the crystalline device. However, in the event that the crystalline devices of the energy transfer luminescence were under high voltage and high brightness, the influence of the purity of the host material on the efficiency of the crystalline OLED devices could be negligible, while its impact on the maximum performance of the crystalline devices was more significant. From this, it can be seen that crystalline devices have an advantage in terms of material cost in the development of device technologies.