Molecular library of OLED host materials—Evaluating the multiscale simulation workflow

Abstract

Amorphous small-molecule organic materials are utilized in organic light emitting diodes (OLEDs), with device performance relying on appropriate chemical design. Due to the vast number of contending materials, a symbiotic experimental and simulation approach would be greatly beneficial in linking chemical structure to macroscopic material properties. We review simulation approaches proposed for predicting macroscopic properties. We then present a library of OLED hosts, containing input files, results of simulations, and experimentally measured references of quantities relevant to OLED materials. We find that there is a linear proportionality between simulated and measured glass transition temperatures, despite a quantitative disagreement. Computed ionization energies are in excellent agreement with the ultraviolet photoelectron and photoemission spectroscopy in air measurements. We also observe a linear correlation between calculated electron affinities and ionization energies and cyclic voltammetry measurements. Computed energetic disorder correlates well with thermally stimulated luminescence measurements and charge mobilities agree remarkably well with space charge–limited current measurements. For the studied host materials, we find that the energetic disorder has the greatest impact on the charge carrier mobility. Our library helps to swiftly evaluate properties of new OLED materials by providing well-defined structural building blocks. The library is public and open for improvements. We envision the library expanding and the workflow providing guidance for future OLED material design.

Virtual Screening for Organic Solar Cells and Light Emitting Diodes

“…Second, high electron/hole mobility is achieved due to zero molecular dipole moment, resulting in small energetic disorder for electron and hole transport. [ 52–55 ] It is also a TADF emitter: it has small Δ E ST (0.016 eV), [ 56 ] achieved by making the donor and the acceptor orthogonal to each other via the m‐xylene bridge. Large $$H_{\text{SO}}^{S_1 T_1}$$ is achieved by exhibiting large differences between excited‐state characters of S 1 and triplet states lying close to S 1 .…”

Chemical design rules for non-fullerene acceptors in organic solar cells

“…To illustrate the practicality of the proposed design criteria, we performed a computational screening on a 121 molecules dataset constructed following the A-D-A design principle with the 11 donors and 11 acceptors shown in Figure 8 1. All donors have inversion symmetry to ensure a small molecular dipole moment, which should facilitate the hole transport of the A-D-A compound [51]. The acceptors are 2methylene-(3-(1,1-dicyanomethylene)indanone) derivatives that have been used in previous studies [52].…”

Virtual Screening of TADF Emitters for Single-Layer OLEDs

“…From a dipolar glass model, the energetic disorder present in a disordered molecular solid is proportional to the dipole moment of the composing molecule. Therefore, thin organic films with molecules with a small dipole moment ( D ) normally have a narrower density of states ( Novikov and Vannikov, 2009 ; Lin et al, 2019 ; Mondal et al, 2021 ; Stankevych et al, 2021 ). This design criteria can be enforced by selecting centrosymmetric molecules only of the D- -A- -D or A- -D- -A type, similar to CzDBA.…”

“…For compounds that pass the screening criteria, the density-of-states distributions for holes and electrons were computed via multi-scale simulations, that include morphology generation using molecular-dynamics simulations, followed by polarizable force-field evaluation of the solid-state contributions to the gas-phase energy levels ( Rühle et al, 2011 ; Poelking and Andrienko, 2016 ; Andrienko, 2018 ; Mondal et al, 2021 ). The entire workflow is illustrated in Figure 3 .…”