A Charge‐Separated State that Lives for Almost a Second at a Conductive Metal Oxide Interface

Abstract

Transparent conductive oxides (TCOs) are widely used commercially available materials for opto‐electronic applications, yet they have received very little attention for dye‐sensitization applications. Now, mesoporous thin films of conductive indium‐doped tin oxide (ITO) nanocrystallites are shown to support long‐lived charge separation with first‐order recombination kinetics (k=1.5 s−1). A layer‐by‐layer technique was utilized to spatially arrange redox and/or chromophoric molecular components on ITO. Spectroelectrochemical measurements demonstrated that upon light absorption, each component provided a free‐energy gradient to direct electron transfer at the conductive oxide interface. The long‐lived nature of the photogenerated charge separated states provide favorable conditions for photocatalytic solar fuel production. Furthermore, the first‐order recombination kinetics are most ideal for the fundamental understanding of interfacial charge separation dynamics.

Dye-sensitized solar cells strike back

“…For fundamental recombination studies, transparent conductive oxide (TCO) materials have some advantages. [119][120][121] They have a metallic character, which permits potentiostatic control of the Fermi level (E F ) and, consequently, of the driving force for charge recombination, ÀDG1 = nF(E1 0 À E F ). Quantifying k cr as a function of ÀDG1 allows analysis through Marcus-Gerischer theory and access to the total reorganization energy (l) and to the electronic coupling.…”

Quantitative insights into charge-separated states from one- and two-pulse laser experiments relevant for artificial photosynthesis

“…The capability of high energy storage is desirable, but too long donoracceptor distances in such systems can counteract a long lifetime of the CSS (see Fig. 2), 11,16,45,52 which is required to exploit the stored energy for subsequent (photo)reactions, 4,53 and are therefore counterproductive for the application in solar energy storage and conversion.…”

Through-Space Conjugation: An Effective Strategy for Stabilizing Intramolecular Charge-Transfer States

“…The in-depth understanding of the intramolecular charge transfer (ICT) state is of high importance for the development of organic optoelectronic materials. − For example, in artificial photosynthesis, the efficient use of sunlight requires the suitable photogenerated ICT states to yield applicable photocurrent. , For dye-sensitized organic solar cells, the ICT state can provide the driving force of the electron transfer . Molecules with electronic donor–acceptor (D–A) structures are widely used for ICT study.…”