Molecular solar thermal energy storage in photoswitch oligomers increases energy densities and storage times

Abstract

Molecular photoswitches can be used for solar thermal energy storage by photoisomerization into high-energy, meta-stable isomers; we present a molecular design strategy leading to photoswitches with high energy densities and long storage times. High measured energy densities of up to 559 kJ kg−1 (155 Wh kg−1), long storage lifetimes up to 48.5 days, and high quantum yields of conversion of up to 94% per subunit are demonstrated in norbornadiene/quadricyclane (NBD/QC) photo-/thermoswitch couples incorporated into dimeric and trimeric structures. By changing the linker unit between the NBD units, we can at the same time fine-tune light-harvesting and energy densities of the dimers and trimers so that they exceed those of their monomeric analogs. These new oligomers thereby meet several of the criteria to be met for an optimum molecule to ultimately enter actual devices being able to undergo closed cycles of solar light-harvesting, energy storage, and heat release.

Donor-Acceptor Substituted Benzo-, Naphtho- and Phenanthro-Fused Norbornadienes

“…This functionalization, however, decreases the energy density (from the optimum 1 MJ kg -1 of the parent system) on account of the increased molecular weight of the molecule. Yet, by using the same aryl group as a bridging substituent between two NBD units, this decrease in energy density can to some extent be counter-balanced [7]. Scheme 1.…”

A UV‐LEDs based photomicroreactor for mechanistic insights and kinetic studies in the norbornadiene photoisomerization

“…Kinetic equations of important intermediates in this photoisomerization can be described by Equations (21)(22)(23)(24)(25)(26), respectively.…”

“…16 In the past decades, many researchers have investigated several homogeneous photosensitizers either dissolved in neat NBD or typical organic solvents (e.g., acetonitrile and p-xylene) as well as heterogeneous photocatalysts, [20][21][22][23][24] and some were interested in discovering proper NBD derivatives that could increase the system capacity of harvesting sunlight. [25][26][27] In this context, the mass transport, photons loss, and photon flux in the photomicroreactor for this photoisomerization were evaluated carefully.…”

Synthesis and Evaluation of Nematicidal Activity of Compounds Derived from Norbornadiene

“…10,11 An area that can be mentioned is its use as a sensitizer in energy production processes. [12][13][14][15] In addition, several reports involving theoretical chemistry for the analysis of the structure and bonds of this kind of compounds are described in literature. [16][17][18] However, there are not reports of norbornadiene and its derivatives as an agrochemical yet.…”