Molecular design of new π-conjugated materials based on pyrimidine for organic solar cellsapplication

Abstract

The research in new π-conjugated molecules with specific applications has become one of the most interesting topics in the fields of chemical physics and materials science.In fact, these compounds have been widely explored, thanks to their essential particular properties, as novel class of promising materials in the field of optoelectronics. In this work, we emphasize the importance of the materials based on pyrimidine π- conjugated derivatives due to their strong potential for solar cell applications. The Density Functional Theory (DFT) approach at B3LYP level and 6-31G(d,p) orbital basis sets for all atoms as implemented in Gaussian 09 program has been used for complete geometry optimization with no constraints of pyrimidine π-conjugated based derivatives.The assessed molecular properties comprise the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and other molecular properties derived from HOMO and LUMO and their respective energies. The absorption spectra were simulated by Time-Dependent Density Functional Theory (TD/DFT) at the B3LYP/6-31G(d,p) level owing to the calculation of the oscillator strengths, the maximum absorption wavelengths and the excitation energy corresponding to the pyrimidine π-conjugated derivatives. The open circuit voltage and the difference between both the LUMO energy levels of the donor and the acceptor have been also evaluated. Hence, we have scanned the rapport, for the molecules under study, between the molecular, the electronic structure and the efficiency of the solar cell in order to give further insights on the possibility of electron transfer between the donor and the acceptor entities. Our results lead to the likelihood to suggest pyrimidine based materials as bulkheterojunction solar cell for organic solar cells application.