Synthesis and design of carbazole-based organic sensitizers for DSSCs applications: experimental and theoretical approaches

The synthesis of two new organic photosensitizers has included furan core as a pi-spacer, ethyl carbazole as a donor, and cyanoacetic acid and cyanoacetohydrazide as acceptors. Organic sensitizers are characterized using electrospray ionization mass spectrometry (ESI–MS), nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopy. Organic sensitizers have been subjected to electrochemical and optical evaluations to examine their absorption behaviour and HOMO/LUMO energies. The optical and electronic properties of dye sensitizers were investigated using density functional theory and the Perdew–Burke Ernzerhof (PBE) functional approach in the present study. The open-circuit voltage, band energy gap, electron injection, reorganization energy, and light harvest efficiency are calculated in both the solvent and gaseous phases. Frontier molecular orbital descriptors such as hardness, electronegativity, electrophilicity index, electron state density diagram, molecular electrostatic potential surfaces, and NMR spectral analysis were computed and addressed in this study. Results of this study show that E)-2-cyano-N'-((5-(9-ethyl-9H-carbazol-3-yl)furan-2-yl)methylene)acetohydrazide (CFCH) and (E)-2-cyano-3-(5-(9-ethyl-9H-carbazol-3-yl)furan-2-yl) acrylic acid (CFCA) organic dye sensitizers have excellent properties for use in dye-sensitized solar cell (DSSCs).