Quantum mechanical calculations of optical absorption of CdS and CdSe quantum dots

Semiconductor CdS quantum dots (QDs) have attracted considerable attention owing to their unusual physical properties from their bulk counterparts and potential applications in non-linear optics, photoelectrochemicals, photocatalysis and single electron transistors. In this work, the optical absorption spectra of CdS and CdSe QDs were calculated quantum mechanically using density function theory. This new development is based on the time independent Schrodinger equation of the ground state energy functional of the Thomas–Fermi–Dirac–Weizsacker atomic system and by algebraically substituted density function in the final Euler–Lagrange equation with the absorption function. The total energy functional was computed numerically for isolated CdS and CdSe QDs having face centred cubic lattice primitive cell structure. The results showed that the CdS and CdSe QD absorption peak increases to higher wavelengths with increasing particle size. The bandgap of the QDs decreases with increasing diameter corresponding to the number of primitive cells needed to construct the particle size.