Stefan Hecht

Humboldt University of Berlin, Germany

The ability to use light to control and power advanced materials and devices in a dynamic fashion with high spatial and temporal resolution offers tremendous opportunities. For this purpose, molecular photoswitches that undergo reversible changes upon illumination have taken center stage and become key ingredients.¹ To develop them into high-performing materials and practical applications, the switching processes must be highly efficient and reliable and therefore necessitate continuing optimization of key parameters. These involve spectral separation and selective addressability in attractive wavelength regions that enable sufficient light penetration, high quantum yields for switching in both directions, enhanced (photo)chemical resistance enabling highly repetitive switching without fatigue, among others. Most importantly, the photoswitchable system has to undergo significant changes of a desired physicochemical property to maximize its overall achievable modulation.

My presentation will introduce the design principles of molecular photoswitches and highlight various examples from our laboratory that illustrate their use to control material properties and device function. Particular emphasis will be on xolography – a volumetric 3D printing method based on photoswitchable photoinitiators recently developed² by us and commercialized by our start-up company xolo.³

1. Goulet-Hanssens A, Eisenreich F, Hecht S, Adv. Mater. 2020, 32, 1905966.
2. Regehly M, Garmshausen Y, Reuter M, König NF, Israel E, Kelly DP, Chou C-Y, Koch K, Asfari B, Hecht S, Nature 2020, 588, 620.
3. www.xolo3d.com