Accurate prediction of inverted singlet-triplet excited states using self-consistent spin-opposite perturbation theory

TL;DR

This paper introduces a computationally efficient method, O2BMP2, for accurately predicting inverted singlet-triplet gaps in molecules, which is crucial for advancing OLED technology and can be used for high-throughput material screening.

Contribution

The study demonstrates that O2BMP2 achieves high accuracy comparable to advanced methods like ADC(3) and EOM-CCSD while reducing computational costs, enabling practical screening of INVEST molecules.

Findings

O2BMP2 accurately predicts inverted singlet-triplet gaps.

The method achieves ADC(3) and EOM-CCSD level accuracy.

Computational complexity can be reduced to N^4.

Abstract

The violation of Hund's rule, resulting in an inverted singlet-triplet (INVEST) gap, represents a paradigm shift in photophysics with major implications for OLED technology. INVEST molecules facilitate barrierless reverse intersystem crossing, theoretically permitting 100\% internal quantum efficiency without thermal activation. However, accurately predicting negative singlet-triplet energy gaps typically demands prohibitive computational costs. In this study, we evaluate the efficacy of our recently developed one-body M{\o}ller-Plesset perturbation theory (OBMP2) and its spin-opposite variant (O2BMP2) as efficient alternatives. Benchmarking against 30 INVEST molecules reveals that O2BMP2, with appropriate spin-opposite scaling, achieves the accuracy of ADC(3) and EOM-CCSD. Furthermore, with the possibility of reducing computational complexity to $N^4$, O2BMP2 provides a robust balance of accuracy and efficiency, making it suitable for the high-throughput screening of next-generation INVEST materials.