In a first part, we analyze the behavior of a skyblue TADF-OLED. The emission zone and the emitter orientation are determined by combining angular emission spectra, measured with Phelos, with optical simulations in Setfos. The characterization of OLED devices with systematically varied hole and electron transport layers using steady-state, transient and impedance measurements allows to gain further insight into device operation. In the second part, we focus on the degradation of the same sky-blue TADF-OLED. Several hypotheses for device degradation were analyzed based on the stress-time dependent behavior in the above mentioned measurements., Presenter: Sandra Jenatsch