Solar energy storage at an atomically defined organic-oxide hybrid interface

Abstract

Molecular photoswitches provide an extremely simple solution for solar energy conversion and storage. To convert stored energy to electricity, however, the photoswitch has to be coupled to a semiconducting electrode. In this work, we report on the assembly of an operational solar-energy-storing organic-oxide hybrid interface, which consists of a tailor-made molecular photoswitch and an atomically-defined semiconducting oxide film. The synthesized norbornadiene derivative 2-cyano-3-(4-carboxyphenyl)norbornadiene (CNBD) was anchored to a well-ordered Co 3 O 4 (111) surface by physical vapor deposition in ultrahigh vacuum. Using a photochemical infrared reflection absorption spectroscopy experiment, we demonstrate that the anchored CNBD monolayer remains operational, i.e., can be photo-converted to its energy-rich counterpart 2-cyano-3-(4-carboxyphenyl)quadricyclane (CQC). We show that the activation barrier for energy release remains unaffected by the anchoring reaction and the anchored photoswitch can be charged and discharged with high reversibility. Our atomically-defined solar-energy-storing model interface enables detailed studies of energy conversion processes at organic/oxide hybrid interfaces.

Molecular photoswitches in aqueous environments

“…387 However, the photochemically generated quadricyclane is a small, light molecule and consists out of five highly strained rings, making the metastable isomer highly energetic and thus an excellent candidate for (solar) thermal energy storage that can be used in films or on surfaces. 388,397,[399][400][401][402][403] By attaching different substituents R (Fig. 27B), the absorption profile of norbornadiene can be tuned up to the green region of the visible spectrum.…”

Storing energy with molecular photoisomers

“…Related model studies were performed using a Co 3 O 4 (111) surface with an atomically defined structure. 118,[120][121][122][123] Monolayer films of NBD derivatives with a carboxylic acid functionality were prepared in which the carboxylic acid group serves as an anchor and binds to the surface Co 2+ ions by forming a chelating surface carboxylate. 120 Using the NBD-derivative 2-cyano-3-(4-carboxyphenyl)norbornadiene (CNBD), the authors prepared a hybrid interface with an anchored QC derivative on Co 3 O 4 (111) in UHV (Figure 6B).…”

New Insight on Photoisomerization Kinetics of Photo-Switchable Thin Films Based on Azobenzene/Graphene Hybrid Additives in Polyethylene Oxide

“…The striking feature of photo-switchable thin films is that the two isomers have different physical and chemical properties. Recently, the azobenzene (AZO) has gained great momentum owing to its potential applications in photochromic molecular switches [ 1 ], light-gated transistors [ 2 ], and molecular solar thermal energy storage media [ 3 , 4 , 5 , 6 ]. AZO has two geometric forms, trans- state and cis -state.…”