Transport and Annihilation of the Triplets in Organic Phosphorescent Systems: Kinetic Monte Carlo Simulation and Modeling

Abstract

We use kinetic Monte Carlo (kMC) simulations to study transport and annihilation of the triplet excitons in organic phosphorescent host–guest systems. By assuming a short-range hopping mechanism for the triplet transport and a long-range dipolar interaction for the triplet–triplet annihilation (TTA), we examine the effect of the relevant experimental parameters on the decay kinetics of the triplets in an energy-disordered system. It is shown that for the range of parameters typical of the organic host–guest systems, transport of the triplets at room temperature is dispersive during their lifetime, with a dispersion exponent of 0.4 < γ < 0.6. We also provide a quantitative comparison between the kMC simulations and the traditional rate coefficients used to describe the TTA. We then suggest and justify a modified rate coefficient that can explain the TTA for a wide range of the system parameters. As the method of analysis, we focus on (a transformed) probability density function of the triplet decay and show that valuable insights into the statistics of the annihilation and the so-called efficiency roll-off can be obtained using this approach. We also discuss how and when describing the annihilation process in terms of an effective time-independent rate can be used to quantify the TTA in the host–guest systems. The results presented in this work are also relevant for other organic devices in which TTA plays a key role in the performance of the system.

Singlet Exciton Dynamics of Perylene Diimide- and Tetracene-Based Hetero/Homogeneous Substrates via an Ab Initio Kinetic Monte Carlo Model

“…Luminescent solar concentrators (LSCs) are devices that use the concept of exciton hopping and total internal reflection to trap light from a large surface area and guide photons to photovoltaic (PV) cells of a smaller surface area. − Here, total internal reflection allows for the transport of energy across macroscopic scales, while exciton dynamics mediate the efficient transfer of energy between molecular bodies, in addition to the recycling of otherwise unusable excitons via multiexciton interactions. − LSCs are obtained by embedding chromophores in a transparent matrix substrate with a large refractive index. When a photon enters the LSC, it is absorbed by a chromophore.…”

Singlet exciton dynamics of perylene diimide and tetracene based hetero/homogeneous substrates via an \textit{ab initio} kinetic Monte Carlo model

“…Luminescent Solar Concentrators (LSCs) are devices which use the concept of exciton hopping and total internal reflection to trap light from a large surface area, and guide photons to photovoltaic (PV) cells of a smaller surface area [1][2][3][4] . Here, total internal reflection allows for transport of energy across macroscopic scales, while exciton dynamics mediate the efficient transfer of energy between molecular bodies, in addition to the recycling of otherwise unusable excitions via multi-exciton interactions [5][6][7][8][9] . LSCs are obtained by embedding chromophores in a transparent matrix substrate with a large refractive index.…”