This study aims to analyze the impact of the alkali metals potassium and rubidium on the nonlinear electronic, thermodynamic, and optical properties of phenacenes (Phn), particularly picene (Ph5), fulminene (Ph6), and [7] phenacene (Ph7). In our work, the doped systems are designated by the general formula, \({M}_{x}Phn\) (M = K, Rb; x = 1, 2; n = 5, 6, 7). A multi-level computational strategy, incorporating ab initio methods, DFT, and TD-DFT, was employed using the 6–311 + G(d) basis set. Optimization of the molecular structures was achieved employing the B3LYP, CAM-B3LYP, and wB97XD functionals. All doped molecules are thermodynamically stable, with the doubly rubidium-doped compound exhibiting the highest stability. The energy gaps of the compounds studied decrease from approximately 4 eV to values below 3 eV. Thus, potassium and rubidium doping significantly reduces the energy gaps, transforming these insulating molecules into semiconductors. Doping also improves nonlinear optical properties. The first-order hyperpolarizability values greatly exceed those of urea. The UV–vis spectra shift toward longer wavelengths after doping. We can say that our new compounds are potential candidates for applications in OFETs, OLEDs, OPVs, and NLOs.
