OLED efficiency model

Organic light emitting diodes (OLEDs) are promising candidates for solid state lighting, but suffer from low efficiency at the high current densities required for such applications. This efficiency decrease is called roll-off, and its mechanism is highly debated. While several contenders have been identified, conflicting studies suggest that the mechanism may be device specific. Identifying the roll-off mechanism for a given device is essential for optimizing the device to improve its efficiency. But there are many different degrees of freedom that can be tuned in an OLED, and both the experimental measurements and the traditional computational tools that would be used to identify the roll-off mechanism are too costly to be used for screening.

We developed a simple, fast model of OLED roll-off, using the mean-field steady state kinetics formalism. This formalism is able to account for disorder in the material in a computationally tractable way. This allows it to reveal the roll-off mechanism in seconds, rather than the days or weeks that a higher level model would need. Such a fast and reliable model will allow for directed optimization of OLED materials that focuses on overcoming the loss mechanism that is specific to a given device, which will reduce the cost of OLED development.

This work was done in close collaboration with Valerie Vassier Welborn, Nadav Geva, and Hayley Weir on the theoretical side, while the experiments were performed by Markus Einzinger. You can read about it here:

1. McIsaac, A.R.; Vaissier Welborn, V.; Einzinger, M.; Geva, N.; Weir, H.; Baldo, M.A.; Van Voorhis, T. Investigation of External Quantum Efficiency Roll-Off in OLEDs Using the Mean-Field Steady-State Kinetic Model. J. Phys. Chem. C, 2020, 124, 27, 14424–14431. link