A systematic investigation to unravel the primary determinant of the operational stability of blue fluorescent organic light-emitting diodes

Abstract

Although it has been long since research on organic light-emitting diodes (OLEDs) began, the root cause of the short lifetime of blue OLEDs remains unclear. We previously reported that electron leakage to the electron blocking layer (EBL) forms excitons with incoming holes, which adversely affect the lifetime of the device. In this study, the most critical factor for the stability of blue fluorescent OLEDs (BFOLEDs) was further investigated through theoretical calculations and experiments by selecting different EBLs, emitting layers (EMLs), and electron transport layers (ETLs) to control charge and exciton dynamics in the EMLs and the EBLs. We found that the lifetime of the BFOLEDs was much more critically impacted by the bond dissociation energy (BDE) in the anionic states of the molecules than by the amount of electron leakage to the EBL. We also revealed that the BDE in the anionic state of the host molecules has a greater impact than that of the EBL molecules.