Role of electronic localization in the phosphorescence of iridium sensitizing dyes

TL;DR

This study investigates how electronic localization affects the excited-state energies of iridium dyes used in optoelectronic devices, employing advanced computational methods to improve understanding and suggest enhancements.

Contribution

The paper compares hybrid functional TDDFT and Hubbard-corrected delta-SCF approaches to analyze electronic localization in iridium dyes, providing new insights into their excited states and charge-transfer characteristics.

Findings

Electronic correlations are crucial for excited-state energies.

Hubbard-corrected functionals reveal electron localization and charge transfer.

Methods agree well with experimental data.

Abstract

In this work we present a systematic study of three representative iridium dyes, namely, Ir(ppy)3, FIrpic and PQIr, which are commonly used as sensitizers in organic optoelectronic devices. We show that electronic correlations play a crucial role in determining the excited-state energies in these systems, due to localization of electrons on Ir d orbitals. Electronic localization is captured by employing hybrid functionals within time-dependent density-functional theory (TDDFT) and with Hubbard-model corrections within the delta-SCF approach. The performance of both methods are studied comparatively and shown to be in good agreement with experiment. The Hubbard-corrected functionals provide further insight into the localization of electrons and on the charge-transfer character of excited-states. The gained insight allows us to comment on envisioned functionalization strategies to improve the performance of these systems. Complementary discussions on the delta-SCF method are also presented in order to fill some of the gaps in the literature.