Fig. 2: Control experiments with model devices and their lifetimes.
From: Critical role of electrons in the short lifetime of blue OLEDs

a Three device setup for control experiments: (a1) a complete electroluminescent device, (a2) an electron-only device with UV illumination, and (a3) an electron-only device with both UV illumination and electric current. HTL and ETL denote hole and electron transport layers, respectively. UV indicates ultraviolet light. b Operational lifetimes of four blue Ir emitters measured in the three experimental setups.