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• The potential energy curve of electronic states have been estimated for the (2) 3 Π − X 3 Π transition of GeC molecule using RKR method. • The radiative transition parameters have been estimated for the (2) 3 Π − X 3 Π transition of GeC molecule. • The effective vibrational temperature helps to ascertain the presence of GeC molecule in sunspot atmosphere. In this work, the experimental potential energy curves for (2) 3 Π and X 3 Π electronic states of GeC molecule have been constructed by using Rydberg-Klein-Rees (RKR) method. The radiative transition parameters viz., Franck-Condon (FC) factor, r-centroid, electronic transition moment, band strength, relative band strength, Einstein coefficients, radiative lifetime and oscillator strength for the (2) 3 Π − X 3 Π system of GeC molecule have been estimated for the experimentally observed vibrational levels from Rydberg-Klein-Rees (RKR) potential and the estimated values are tabulated. The estimated effective vibrational temperature found as 5628 K for the (2) 3 Π − X 3 Π system of GeC molecule. The radiative transition parameters and effective vibrational temperature are evident that the possible presence of GeC molecule in solar and sunspots atmosphere. Further, these parameters are employed in rationalizations of astrochemical and astrophysical observations. [ABSTRACT FROM AUTHOR]

[Display omitted] • There are smaller energy gap, larger SOC and more limited geometric structure changes in solid-phase environment. • The effective ISC and RISC processes between S 1 and T 2 reveal the TADF mechanism of PyB-DPAC. • The superior AIE property benefits from the suppressed non-radiative process and enhanced radiative transition. An investigation of high-performance organic green thermally activated delayed fluorescence (TADF) material, PyB-DPAC, with aggregation-induced luminescence (AIE) characteristics was theoretically conducted by the first principle calculations method in this work. The polarizable continuum mode (PCM) and the combination of quantum mechanics and molecular mechanics (QM/MM) method were employed to consider the liquid-phase and solid-phase environments, respectively. Results show that TADF mechanism of the molecule is mainly due to the occurrence of efficient intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes between S 1 and T 2 , which benefits from the small energy gap, large SOC and the limited changes of molecular geometry structures in solid-phase environment. The increase of radiative transition rate (K r) and significant decrease of non-radiative transition rate (K nr) is responsible for the AIE property. Our calculations reasonably explained the experimental results and showed that PyB-DPAC is an excellent TADF material with AIE characteristics, this may help to better understand the influence of solid-state effect and the luminescence mechanism of AIE-TADF molecules. [ABSTRACT FROM AUTHOR]