Boron fullerenes, Bn (n=20, 30, 38, 40, 50, 60): First principle calculations of electronic and optical properties.

Density functional theory (DFT) and time dependent density functional theory (TDDFT) at PBE0/6-311G* level are performed to examine the stability, electronic and optical properties of boron fullerenes (Bn, n = 20, 30, 38, 40, 50, 60). Amongst all the structures, B50 is found to be highly stable and has the least electronic gap. In general, all borofullerenes are found to be semiconducting in nature. Absorption wavelength shift in the photoabsorption spectra is reported with the increasing borofullerene size. Furthermore, the maximum absorption occurs within the visible range (for n = 30-50) characterized by deeper level excitations. Upon absorption, the electron delocalization is found to increase with the borofullerene, from natural transition orbital analysis (NTO) and exciton size analysis, respectively. Exciton size determination indicates a linear relationship between the number of borofullerene atoms and the exciton size. The excitons have been found to be Frenkel in nature.