Abstract
First principle calculations were carried out to investigate the electron injection, electron coupling, electronic, and photophysical properties of two coumarin derivatives coumarin 102 and coumarin 153. The initial molecular geometries of both derivatives were optimized in the ground state using density functional theory in conjugation with B3LYP functional and 6-31G(d,p) basis set. The highest occupied molecular orbital (HOMO) of coumarin 102 and coumarin 153 were observed beneath the redox couple, whereas the lowest unoccupied molecular orbital (LUMO) of both coumarin derivatives were observed above the conduction band of TiO2. The time-dependent density functional theory has been used to calculate the excitation energies at PCM-CAM-B3LYP/6-31G(d,p) level. Based upon the calculation of hole reorganization energy lambda(h) and electron reorganization energy lambda(e), it has been observed that both coumarin 102 and coumarin 153 are hole transport materials. The electronic coupling constant, electron injection, and light harvesting efficiencies of these coumarin derivatives are higher than coumarin. This clearly indicates that these derivatives would be excellent photosensitizers. Finally, the effect of electric field on the dipole moment, HOMO, LUMO, and HOMO-LUMO gap has been thoroughly observed to check the competency of these derivatives for the possible use in organic field effect transistors.