Strategic Design of Bacteriochlorins as Possible Dyes for Photovoltaic Applications

Bacteriochlorin-based dyes, having a push-pull type of configuration similar to that of the YD2 dye, were theoretically designed based on modification of the macrocycle and π-conjugated bridge for use in dye-sensitized solar cells. Various parameters were assessed to determine its structure-property relationships, such as the absorption profile based on time-dependent density functional theory, nonlinear optical properties from (hyper)polarizability data, ground- and excited-state oxidation potentials, and the electronic properties of the free and adsorbed dyes. On the basis of the results, the most appropriate macrocycle would be 7,7,17,17-tetramethyl-7H,8H,17H,18H-porphyrin and, for its π-conjugated bridge, either thieno[3,2-b]thiophene, dithieno[3,2-b:2',3'-d]thiophene, or 4,4-diisopropyl-4H-cyclopenta[2,1-b:3,4-b']dithiophene. These newly designed dyes produced an absorption spectra having a range of 300-800 nm, which could likely increase the light harvesting efficiency. It has better nonlinear properties than the reference, thereby ensuring higher charge-transfer properties. Also, the dye regeneration efficiency is within the optimized value of 0.2 eV, which could minimize the excessive loss of voltage. This shows that through theoretical approach we can deductively design analogues before synthesis to streamline the process in the design of dyes to produce efficient dye-sensitized solar cells.