Molecular engineering of the efficiency of new thieno[3,2-b]thiophene-based metal-free dyes owning different donor and π-linkers groups for use in the dye-sensitised solar cells: a quantum chemical study

Abstract

ABSTRACT In this work, the new metal-free organic donor-π-acceptor (D-π-A) D1-3L1-4 dyes formed from 2-cyanoacrylic as the electron acceptor (anchoring) group were investigated. Density functional theory (DFT) and time-dependent DFT (TD-DFT) were used to evaluate the electronic, structural, and optical properties of the organic dyes. The theoretical results show that the trend of the calculated HOMO–LUMO energy gap is in good agreement with the photophysical data. Key parameters of the sensitisers in the dye-sensitised solar cell devices associate with the short-circuit current density (Jsc), electron injection driving force ΔGinject, total reorganisation energy λtotal (λh and λe), light-harvesting efficiency (LHE), and open circuit potential (Voc) were explored. The results show that increasing the length of π–bridge has a significant effect on the electronic and optical properties of dyes. Further, donor moieties have a strong effect on the performance of dyes. Based on the obtained results, the D3L3 and D3L4 dyes could improve the light-harvesting efficiency, intramolecular charge transfer parameters, and electron injection efficiency. The results of this work can provide valuable insight into the design of DSSCs with high-efficiency.