Evidence for localized trap formation during TADF OLED degradation

Edoardo Stanzani, Stefano Sem, Simon Züfle, Beat Ruhstaller, Sandra Jenatsch,

Organic Electronics, Volume 139, 2025, 107204, ISSN 1566-1199,

https://doi.org/10.1016/j.orgel.2025.107204.

This research lead by joint first authors Edoardo Stanzani and Dr. Stefano Sem and with the support of the Fluxim research team investigated the degradation mechanisms of thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). By combining experimental measurements with device simulations, the study identifies the formation of hole and electron traps at the HTL/EML interface as the primary cause of efficiency reduction. The researchers pinpoint hole traps within the hole transport layer (HTL) as the main contributor to the OLED's decreased performance. Their findings offer crucial insights into enhancing the operational stability of TADF OLEDs, aiming to extend their lifespan for use in commercial displays.

Summary of Setfos, Paios, and Litos Use:

Setfos was used to model the electrical characteristics of the OLED devices. The software employed a charge carrier drift-diffusion model, and was used to simulate the impact of trap states on the device performance. Device simulations helped to assess the location of trap states within the multilayer structure by comparing simulated and experimental capacitance values.

Paios: This all-in-one measurement platform was used for intermittent electro-optical characterizations. These measurements included current-voltage (JV), capacitance-frequency (C-f), and capacitance-voltage (C-V) scans. Paios enabled in-situ testing without disconnecting the samples, by being connected to Litos.

Litos was used to stress the OLED devices under constant current. During the stressing, the voltage and emission signals were recorded. The Litos system was connected to Paios for in-situ intermittent testing.

In summary, Litos stressed the devices, Paios characterized them intermittently, and Setfos simulated the device behavior to help understand the degradation mechanisms.