Disentangling degradation and auto-recovery of luminescence in Alq3 based organic light emitting diodes

Organic semiconductor devices and materials have matured sufficiently to be limited by intrinsic degradation processes which are as yet not understood well. We use high quality Alq3 based organic light emitting diodes to study the rate processes involved in degradation due to electrical stressing and its auto-recovery. The method involves interspersing degradation due to electrical pulsing with variable relaxation windows to monitor time evolution of loss and recovery of luminescence. The corresponding rate processes for permanent and auto-recoverable degradation is discussed on the basis of charging and discharging of traps, and a phenomenological model based on metastability in configuration-coordinate diagram is proposed.