Designing and Study of New Small Molecules Based Thiophene as Donor Materials for Bulk Heterojunction Photovoltaic Cells

Abstract In this research work, we study the structural, optical, electronic and photovoltaic properties of eight thiophene-based π-conjugated organic molecules using quantum methods namely time-dependent density functional theory(TD-DFT). In particular, we identify the relationships between the chemical structure of these π-conjugated organic molecules and their optoelectronic properties. Moreover, we calculate and compare the highest energy occupied molecular orbital (HOMO) and lowest energy unoccupied molecular orbital (LUMO) energy levels of these compounds to that of the PCBM.As a result, the investigated molecules show a low band gap, suitable open circuit voltage and appropriate alignment energy level between the engineered donor molecules and the acceptor PCBM. This theoretical study shows that these new molecules have potential properties for the development of organic heterojunction photovoltaic cells.