Rapid Estimation of fwhm for OLED Emission Spectra Using Bond-Length and Bond-Order Alterations

Color purity is crucial for achieving
a high-quality
organic light-emitting
diode. An essential property for evaluating color purity is the full
width at half-maximum (fwhm) of emission spectra. Theoretically estimating
fwhm requires the detailed knowledge of vibronic coupling constants
for all vibrational modes, which is time-consuming to obtain via quantum
mechanical calculations, particularly for optimizing the geometry
of the lowest singlet excited state. These calculations pose a bottleneck
for high-throughput screening of narrowband emitters. To address this
challenge, we propose a simple model to assess the reorganization
energy based on the relationship between bond-length alteration (ΔBL)
and vertical bond-order alteration (ΔBO) in optimized ground-state
structures. Additionally, a one-mode model is employed to rapidly
and effectively estimate fwhm. Our new model yields results comparable
to experimental data and more accurate theoretical approaches based
on vibronic coupling constants of all vibrational modes but with significantly
lower computational costs. This model holds promise for the virtual
screening of narrowband emitter candidates.