New D-π-A type indole based chromogens for DSSC: Design, synthesis and performance studies

• Three new Donor-π-Acceptor type dyes based on indole, carrying three different acceptor units were designed and synthesized.
• The dyes show broad absorption capacity with high molar extinction coefficient.
• The single crystal X-ray diffraction study confirms the planarity of the molecules.
• EIS and CV measurements as well as DFT calculations indicate that molecules exhibit good charge transfer properties.
• The profound effect of different acceptor groups on the overall efficiency of DSSC was extensively studied.

Three new Donor-π-Acceptor type dyes D1–3 carrying 3-(1-hexyl-1H-indol-3-yl)-2-(thiophen-2-yl)acrylonitrile as backbone with three different acceptor units were designed and synthesized as promising sensitizers for solar cell application. The new dyes were characterized using various spectral and elemental analyses. Their optical and electrochemical properties were investigated using spectrophotometry and cyclic voltammetry respectively, while their photovoltaic performance was evaluated by a device fabrication study. The devices were subjected to electrochemical impedance spectroscopy to gain an insight into the interfacial charge transfer and recombination process while in use. Further, density functional theory study was carried out to investigate their Frontier Molecular Orbital energy states. The study reveals that the dye carrying 4-aminobenzoic acid as an acceptor showed the highest photovoltaic efficiency among the three dyes. This can be attributed to the longer electron lifetime and lower recombination rates. Additionally, a Single crystal X-ray diffraction study confirmed the structure of a key intermediate.

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