Tuning optical absorption in pyran derivatives for DSSC

• We synthesized four nobel metal free photosensitizers for DSSC.
• Dyes are based on a pyran acceptor core symmetrically linked to carbazole donor groups.
• Dyes show colors ranging from orange to blue, covering the most of visible spectrum.
• The electronic structure of the dyes were investigated at DFT level.
• DSSC based on the reported chromophores show power conversion efficiency up to 1.9%.

Four nobel metal free dyes for application as photosensitizers in DSSC have been synthesized and their chemical–physical properties characterized by UV–vis absorption spectroscopy, cyclic voltammetry and DFT theoretical computations. The dyes are based on a pyran core, functionalized with different electron acceptor groups, symmetrically linked to carbazole electron donor mojeties. The four dyes have different optical absorption properties, affording a range of colors ranging from orange to blue, covering most of the visible spectral region. All the dyes feature high molar extinction coefficient, up to a value of 1.0 × 105 L mol−1 cm−1. The dyes were used as photosensitizers in DSSC and the photovoltaic characterization of these devices was performed under simulated solar radiation. The cell performance is higher for chromophores featuring higher LUMO energies as a consequence of a better electron injection in TiO2 oxide. A maximum power conversion efficiency of 1.9% has been achieved.

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