Enhanced performance in inverted organic light emitting diode assisted by an interlayer of crystalline and n-doped 1,4,5,8-naphthalene-tetracarboxylic-dianhydride

Inverted bottom-emission organic light emitting diodes (IBOLEDs) employing the electron injection structure of indium tin oxide (ITO)/1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA)/Li2CO3 doped bathocuproine (BCP) (1: 4 Li2CO3: BCP) were fabricated, where NTCDA and BCP stand for NTCDA and BCP, respectively. The NTCDA on ITO was characterized crystalline and n-doped as a result of the interaction between ITO and NTCDA. Compared to the IBOLED using the electron injection structure of ITO/10 nm 1: 4 Li2CO3: BCP, the one utilizing the electron injection structure of ITO/3 nm NTCDA/7 nm 1: 4 Li2CO3: BCP showed the remarkable increases in both current density and efficiency, mainly due to the higher electron conductivity of n-doped NTCDA than that of n- doped BCP. The dependence of the current conduction in IBOLED on the thickness of NTCDA was investigated. We provide a simple method to significantly enhance the performance of IBOLEDs.