Improving the performance of organic light-emitting devices by incorporating non-doped TCNQ as electron buffer layer

The performance of organic light-emitting devices (OLEDs) is improved by inserting non-doped tetracyanoquinodimethane (TCNQ) electron buffer layer (EBL) between 4,7-diphnenyl-1,10-phe-nanthroline (Bphen) electron transport layer (ETL) and LiF/Al cathode. By optimizing the thickness of TCNQ layer, we find that the device with 6 nm TCNQ buffer layer can achieve the best performance. The maximum luminance, current efficiency, power efficiency and half-lifetime of the optimal device are increased by 27.32, 51.70, 127.55, and 73.89%, respectively, compared with those of the control device without TCNQ buffer layer. This improvement can be attributed to that the insertion of non-doped TCNQ buffer layer which is a simple approach can enhance the electron injection and operational stability of the devices. Moreover, we have carried out the tests of the atomic force microscope (AFM), scanning electron microscopy (SEM) and Kelvin probe to explore the effect of insering TCNQ. These tests results further verify that TCNQ layer not only smooth the surface of the films but also improve the electron injection and transport characteristics. As a result, the performances of the OLEDs can be effectively improved.