Energy-Loss Reduction as a Strategy to Improve the Efficiency of Dye-Sensitized Solar Cells

Four weak donor backbones (BT, BTP, BT2, and BT3), featuring stepwise enhanced electron-donating capacities, are designed and synthesized. The sp 3 type carbons introduced are tethered with auxiliary groups to generate a better electron-blocking stereoscopic structure. A series of NB dyes are subsequently synthesized from these central cores by end-capping a strong diphenylamine donor and a planar heterocyclic acceptor 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid. The fine-tuning of steric configurations and energy levels of the resulting dye molecules reduces the energy losses significantly when applied in dye-sensitized solar cells. These devices offer one of the highest open-circuit voltages (≈1.03 V) reported so far, and high power conversion efficiencies of 9.6%–12.1% using the NB dyes in combination with a well-developed cobalt-tris(4-methoxyphenyl)amine-based tandem electrolyte.