Using supramolecular machinery to engineer directional charge propagation in photoelectrochemical devices

Abstract

Molecular photoelectrochemical (PEC) devices are hampered by electron-hole recombination after photoinduced electron transfer (PET), causing losses in power conversion e ciency (PCE). Inspired by natural photosynthesis, we demonstrate the use of molecular machinery as a strategy to inhibit recombination, through organization of molecular components and unbinding of the nal electron acceptor after reduction. We show that preorganization of the macrocyclic 3-NDI-ring electron acceptor to the P STATION dye forming the P STATION :3-NDI-ring pseudorotaxane, enables a "ring launching" event, upon PET from P STATION to 3-NDI-ring releasing 3-NDI-ring •− . Implementing P STATION :3-NDI-ring into p-type dyesensitized solar cells (p-DSSCs) revealed a vefold increase in PCE compared to benchmark dye P1, unable to facilitate pseudorotaxane formation. This active repulsion of anionic 3-NDI-ring •− with concomitant reformation P STATION :3-NDI-ring circumvents recombination at semiconductor-dye interface, affording a twofold enhancement in hole lifetime. We envision this concept of supramolecular-directed charge-propagation will encourage further integration of molecular machinery into PEC devices.

The Green Box: Selenoviologen-Based Tetracationic Cyclophane for Electrochromism, Host–Guest Interactions, and Visible-Light Photocatalysis

“…In addition, the color and spectroelectrochemistry of ECDs using 3⊃G1 or 5⊃G1 as active ingredients showed three states when external voltages were applied, suggesting a transformation from a tetracationic complex to biradical dicationic cyclophane and free G1, and then to a neutral cyclophane (Figures 53 and S65). 4,70 Finally, the 5⊃G1-based ECDs showed higher radical stability than that of free 5 and 3⊃G1, respectively (Figures S54 and S66).…”

The Role of Dethreading Process in Pseudorotaxanes and Rotaxanes towards Advanced Applications: Recent Examples

“…[90] The formation of pseudorotaxanes in DSSC was also employed by Reek and coworkers as a method to improve their efficiency. [91] The pseudorotaxanes were constituted by the ptype dye-based thread 18 bearing 1,5-dioxynaphthalene bind- [83] The key colour of the cartoon representation is analogous to that of the chemical structures.…”

“…Figure 8. a) Chemical structures of dye-based thread 18 and macrocycle 19; and b) cartoon representation of the operation of the pseudorotaxane-based DSSC [91]. The key colour of the cartoon representation is analogous to that of the chemical structures.…”

Charge Recombination Deceleration by Lateral Transfer of Electrons in Dye-Sensitized NiO Photocathode

“…Pioneering studies on n-type (mainly TiO 2 ) DSSCs have demonstrated that the addition of a secondary electron donor to the dye, to shift the hole further from the semiconductor after electron injection, can significantly slow down recombination. − The corresponding approach with dye–acceptor dyads on NiO led to as much as ca . five orders of magnitude retardation of charge recombination moving from an ∼100 ps to an ∼10 μs time scale; ,, related effects have since been reported. − The large difference cannot be simply explained in terms of variation in reaction free energy or the distance factors. Furthermore, with dyes and molecular proton reduction catalysts co-adsorbed on NiO, rapid (∼10 ps) electron transfer from the dye to the catalyst was observed after hole injection, which led to charge recombination on the ∼10 μs time scale. , This strong retardation is difficult to explain just based on the properties of the dyes and catalysts.…”