Theoretical investigation of novel electron donors for bulk heterojunction solar cells with potential photovoltaic characteristics.

Engineering electronic organic donor materials are one of the most critical steps in producing bulk-heterojunction solar cells (BHJ) with good photovoltaic properties. Compared to standard donor materials, electron donors derived from thiophene have made significant progress as they can be better suited for optoelectronics and are cheaper and more stable. Therefore, the use of new thiophene derivatives (M1-M4) as donor molecules in BHJs has been the subject of this extensive theoretical analysis. Density functional theory (DFT) and time-dependent DFT (TD-DFT) computations have been used to investigate the boundary molecular orbital (FMO) analysis, the density of states analysis, electron and hole reorganization energy, molecular electrostatic potential, global reactivity parameters, and photovoltaic properties. The effects of end-donor modifications on the photovoltaic and electronic characteristics of the new molecules (M1-M4) are investigated. According to the results, the molecules have good optical properties, a small band gap, a perfect open-circuit voltage, and a good alignment energy level between the designated donor molecules and the acceptor phenyl-C61-butyric acid methyl ester (PCBM). These results suggest that further research in this area could enhance the efficacy of organic solar cells.

Electronic and optical aspects of novel quinoxaline derivatives as electron donor materials for bulk heterojunction solar cells.

In this paper, we design new forms of organic conjugated compounds-based quinoxaline derivatives. Specifically, we exploit density functional theory and time-dependent-density functional theory in order to study the structure, the optic, the electronic, the reorganization energy and the photovoltaic features of such new molecules. Particularly, all engineered compounds have a narrow band gap in the range of 0.696-0.721 eV, high oscillator frequency and good optical properties. Moreover, the PCBM is employed as an electron acceptor. Employing global reactivity descriptors, we demonstrate that the molecules can efficiently emit electrons into the PCBM and the electrons are attracted to PCBM from molecules. In addition, the results show an appropriate open circuit voltage in the range of 0.338-0.362 V. The proposed compounds exhibit excellent electron transport and charge conduction from the donor to the acceptor. These new molecules show potential properties to develop bulk heterojunction organic photovoltaic cells.

Computational Study of New Small Molecules based Thiophene as Donor Materials for Bulk Heterojunction Photovoltaic Cells.

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. 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 and lowest energy unoccupied molecular orbital energy levels of these compounds which act as donor with the ones of the acceptorphenyl-C61-butyric acid methyl ester. 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 phenyl-C61-butyric acid methyl ester. This theoretical study shows that these new molecules have potential properties for the development of organic heterojunction photovoltaic cells.

Physical and chemical aspects of the interaction of chitosan and cellulose acetate with ions Ca2+ and K+ using DFT methods.

Motivated by the use of chitosan (Ch), and cellulose acetate (AC) as organic matrices in several therapeutic drugs, a theoretical study has been elaborated through the density functional theory method (DFT) to investigate the interaction mechanism between two essential ions for the human body Ca2+, K+ and two organic matrices chitosan (Ch), and cellulose acetate (AC). Many physical and chemical aspects have been carried out after the achievement of structural optimization. This involves structural parameters, molecular electrostatic potential (MEPs), interaction energy, reactivity indexes, frontier molecular orbitals (FMOs), quantum theory atoms in molecules (QTAIM) analysis, and non-covalent interaction (NCI) analysis. The results of FMOs, MEPs, and reactivity index studies have revealed that the site of interaction can be predicted. The calculation of electron interaction energies shows that those ions interact with the matrix of AC and Ch. Concretely, the Ca2+ ion interacted efficiently with the AC matrix. The structural analysis results show that the interaction of Ch and ions appear spontaneously (ΔG < 0) while the interaction of AC and ions (ΔG >0) requires more energy to occur. Finally, the QTAIM analysis data indicates that the interactions of AC-ions and Ch-ions are non-covalent presenting an electrostatic character.