On the theoretical prediction of fluorescence rates from first principles using the path integral approach

Abstract

In this work, we present and implement the theory for calculating fluorescence rates and absorption and emission spectra from first principles, using the path integral approach. We discuss some approximations and modifications to the full set of equations that improve speed and numerical stability for the case when a large number of modes are considered. New methods to approximate the excited state potential energy surface are also discussed and it is shown that for most purposes, these can be used instead of a full geometry optimization to obtain the rates mentioned above. A few examples are presented and the overall performance of the method is discussed. It is shown that the rates and spectra computed in this way are well within the acceptable range of errors and can be used in future predictions, particularly for screening purposes, with the only limitation on size being that of the electronic structure calculation itself.

Persistent Solid‐State Phosphorescence and Delayed Fluorescence at Room Temperature by a Twisted Hydrocarbon

“…Combining our path‐integral approach with the SOC results, we could simulate the emission spectra for both the fluorescence and phosphorescence (Figure ) within a reasonable TD‐DFT error. The predicted results are in good agreement with the experimental data, thus confirming the coexistence of long‐wavelength phosphorescence with short‐wavelength DF.…”

The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes

“…This dichotomy of stable, uorescent and reactive, non-uorescent chromophores is also reected in the theoretical modeling of those compounds: when uorescence is dominant, the harmonic approximation is invoked and transitions (both radiative and non-radiative) between the harmonic potential energy surfaces of the initial and nal electronic states are accounted for by perturbation theory. [15][16][17][18] On the other hand, photochemical reactions require different approaches such as non-adiabatic molecular dynamics simulations, where the nuclei are treated as classical particles rolling on and jumping between potential energy surfaces. [19][20][21][22][23][24] Such simulations, however, are limited to short timescales, not more than a few hundred femtoseconds, while typical experimental uorescence lifetimes are in the order of nanoseconds.…”

New Boron(III) Blue Emitters for All‐Solution Processed OLEDs: Molecular Design Assisted by Theoretical Modeling

“…Trying to overcome these limitations, boron(III) complexes with the widely used ligand 2‐(benzothiazol‐2‐yl)phenol (HBT) were recently synthesized. They displayed high Stokes shifts and high fluorescence intensities at the same time, and their emission color was shown to be tunable through chemical modifications on the aromatic moiety …”

“…Calculations using DFT assisted molecular and electronic structure interpretation, as well as some excited state dynamics. We show that our recently developed formalism in conjunction with time‐dependent density functional theory (TD‐DFT), allows the prediction of emissive rates and the fluorescence spectra with impressive accuracy. Finally, the complexes were dispersed on a double‐host emissive layer and all solution processed OLEDs were prepared.…”