Rapid Estimation\nof fwhm for OLED Emission Spectra\nUsing Bond-Length and Bond-Order Alterations

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