Discovery of versatile bat-shaped acceptor materials for high-performance organic solar cells - a DFT approach

To address the growing demand for competent photovoltaic materials, the electronic structure, and optoelectronic properties of eight molecules X1 (thieno[3,2-b]thiophene), X2 (5,5'-bithiazole), X3 (2,2'-bithiophene), X4 (furan), X5 (1H-pyrrole), X6 (furo[3,2-b]furan), X7 (5-(1H-imidazol-5-yl)oxazole), X8 (3H,3'H-4,4'-biimidazole) designed via pi-spacer modification were investigated by extensive density functional theory (DFT) based calculations. The calculated HOMO-LUMO energy (E-g) values of these designed molecules are less than alkoxy-substituted benzothiadiazole and a rhodamine end group reference (R, E-g = 2.55 eV), whereas X8 shows the lowest (E-g = 2.17 eV) suggesting a greater charge transfer rate upon blending with donor polymer PTB7-Th. The values of open-circuit voltages for designed molecules are 2.30, 2.52, 2.23, 2.52, 2.37, 2.19, 2.53, and 2.18 V for X1-X8, respectively, where X3, X6, and X8 shown lower voltages than the reference R (2.30 V). Similarly, the 0.13 eV difference of reorganization energy value of X1 compared to reference R, demonstrates higher charge transfer by X1 due to its lower hole mobility. The findings suggest potentially superior performance of organic solar cells (OSCs) fabricated with the designed molecules (X1-X8).

Automated summary

Molecules designed with π-spacer modification have potential advantages in photovoltaic materials and are suitable for the fabrication of organic solar cells.