Modeling charge recombination in dye-sensitized solar cells using first-principles electron dynamics: effects of structural modification.

We have performed real-time excited state simulations of electron injection and charge recombination at a dye/semiconductor interface within the framework of time-dependent density functional theory (TDDFT). We found that by inserting a phenyl ring into the organic dye, the charge recombination rate is slowed down by about four times, while the injection rate keeps almost the same. This introduces a drastic increase in the energy conversion efficiency by several folds, in agreement with experimental observations. Quantum simulations thus provide a new way to understand the role of the dye's building blocks and offer new strategies to optimize individual energy transfer steps for improving the efficiency in renewable energy applications.