The use of single molecules in electronics represents the next limit of miniaturisation of electronic devices, which would enable to continue the trend of aggressive downscaling of silicon-based electronic devices.

This review delineates the developments in triplet–triplet annihilation based NIR to Vis molecular photon upconversion including recent progress in conceptual design, applications, existing challenges, possible future directions and opportunities.

This perspective discusses recent progress in photon upconversion systems and devices for solar energy applications.

Solar energy conversion and solar energy storage are key challenges for a future society with limited access to fossil fuels. Certain compounds that undergo light-induced isomerisation to a metastable isomer can be used for storage of solar energy, so-called molecular solar thermal systems. Exposing the compound to sun light will generate a high energy photoisomer that can be stored. When energy is needed, the photoisomer can be catalytically converted back to the parent compound, releasing the excess energy as heat. This Letter gives examples of selected molecular solar thermal systems found in the literature. The focus of the Letter is on examples where molecular design has been used to improve the performance of the molecules, and as such it may serve as an inspiration for future design. The selected examples cover five widely studied systems, notably: anthracenes, stilbenes, azobenzenes, tetracarbonyl-fulvalene-diruthenium compounds and norbornadienes

A device for solar energy storage and release based on a reversible chemical reaction is demonstrated. A highly soluble derivative of a (fulvalene)diruthenium (FvRu₂) system is synthesized, capable of storing solar energy (110 J g⁻¹) in the form of chemical bonds and then releasing it “on demand”, when excited thermally or catalytically. A microfluidic device is designed and constructed for both the photo-harvesting and the heat-utilization steps, allowing for the recycling of material.