Theoretical Study of WS-9-Based Organic Sensitizers for Unusual Vis/NIR Absorption and Highly Efficient Dye-Sensitized Solar Cells

Abstract

Dye-sensitized solar cells (DSSCs) are the most promising low-cost photovoltaic devices. Whereas, the absorption bands of most organic sensitizers, the most vital component in DSSCs, are limited to a relatively narrow visible range. To obtain efficient sensitizer, a series of D–A−π–A metal-free dyes have been designed based on one of the best sensitizers WS-9 by modifying auxiliary acceptor and characterized theoretically. The results illustrate that introduction of auxiliary heterocycle acceptor is revealed to very narrow band gap (HOMO–LUMO), leading to an obvious red-shifted broad near-infrared absorption band in the range of 750–1950 nm compared to WS-9 (536 nm). The critical parameters in close connection with the short-circuit current density (Jsc), open circuit voltage (Voc), including singlet excited state lifetime (τ), total dipole moments (μnormal), the conduction band of edge of the semiconductor substrate (ΔECB), and regeneration driving forces (ΔGreg) are superior to those of WS-9. Therefore, these novel sensitizers would be a promising candidate for improving the performance of the DSSCs.