We demonstrate the importance of a comprehensive modeling of the dynamics of excited states in organic optoelectronics devices. Our numerical analysis demonstrates that exciton distributions extracted from spectral emission measurements of OLEDs are equivalent to those obtained by solving charge and exciton transport equations when the position-dependent coupling to optical modes is taken into account. The transport simulations are based on the extended Gaussian disorder model for organic semiconductors. Further, we show that the same numerical modeling framework can be used to accurately simulate bulk-heterojunction organic solar cells with dissociation of charge-transfer excitons. The simulations are compared to experimental data.
In this paper, we introduce an extension of the coupled electronic-optical model to simulate organic light-emitting
devices (OLEDs). We couple the influence of the optical environment to the exciton transport equation which
yields a position dependent exciton lifetime. Thereby we get a more accurate spatial distribution of excitons,
namely the emission profile. We show that the emission profile is dependent on the intrinsic quantum efficiency.
In a second part of this paper, an extended numerical algorithm for extraction of the emission profile from
emission spectra is presented. The extended extraction algorithm takes the influence of the optical environment
into account. We call it the excitonic lifetime fitting method (ELF) and compare it to a conventional linear
fitting method. On the basis of consistency checks we demonstrate the influence of noisy emission spectra and
device thicknesses. Our investigations show the impact of the ELF method, which improves the accuracy and
robustness of the extracted emission profile considerably up to 120 %.
A comprehensive electronic-optical simulation tool for the design of complex organic multi-layer device structures is
presented. The physical models comprise the key optical and electronic processes governing organic light-emitting
(OLEDs) and light-harvesting devices. The simulation of such devices is demonstrated for electronic-only or optics-only
models as well as for electronic-optical and optical-electronic coupled device models. Validation examples with
experimental data and applications for device simulations are also discussed. It is shown that both light-emitting and
light-harvesting devices require careful optical as well as electronic multilayer design and characterization.