Near-infrared absorption of fused core-modified expanded porphyrins for dye-sensitized solar cells

• Published in: The Journal of chemical physics 2023-04, Vol.158 (16)
• Main Authors: Menéndez, María Isabel, Montenegro-Pohlhammer, Nicolas, Pino-Rios, Ricardo, Urzúa-Leiva, Rodrigo, Morales-Lovera, Simone, Borges-Martínez, Merlys, Granados-Tavera, Kevin, López, Ramón, Cárdenas-Jirón, Gloria
• Format: Article
• Language: English
• Subjects: Charge transport; Density functional theory; Dye-sensitized solar cells; Dyes; Electrolytic cells; Infrared absorption; Near infrared radiation; Photovoltaic cells; Porphyrins; Pyrroles; Solar energy; Thiophenes; Titanium dioxide; Transport properties
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/5.0143835

Photophysical, photovoltaic, and charge transport properties of fused core-modified expanded porphyrins containing two pyrroles, one dithienothiophene (DTT) unit, and 1–4 thiophenes (1–4) were inspected by using density functional theory (DFT) and time-dependent DFT. Compounds 1–3 have been investigated experimentally before, but 4 is a theoretical proposal whose photophysical features match those extrapolated from 1 to 3. They exhibit absorption in the range of 700–970 nm for their Q bands and 500–645 nm for their Soret bands. The rise of thiophene rings placed in front of the DTT unit in the expanded porphyrin ring causes a bathochromic shift of the longest absorption wavelength, leading to near-infrared absorptions, which represent 49% of the solar energy. All the systems show a thermodynamically favorable process for the electron injection from the dye to TiO2 and adsorption on a finite TiO2 model. The electron regeneration of the dye is only thermodynamically feasible for the smallest expanded porphyrins 1 and 2 when I−/I3− electrolyte is used. The charge transport study shows that for voltages lower than 0.4 V, junctions featuring pentaphyrin 1 and octaphyrin 4 are more conductive than those containing hexaphyrin 2 or heptaphyrin 3. The results showed that the four fused core-modified expanded porphyrins investigated are potential dyes for applications in dye-sensitized solar cells, mainly pentaphyrin 1 and hexaphyrin 2. Moreover, increasing the number of thiophene rings in the macrocycle proved fruitful in favoring absorption in the near-infrared region, which is highly desired for dye-sensitized solar cells.