Blue-to-UV up-conversion with lanthanide ions

While efficient semiconductor-based LEDs have been available for the visible range since the 1990s at the latest (which also resulted in the 2014 Nobel Prize in Physics), only cost-intensive, large and, in some cases, environmentally unfriendly solutions for efficient lighting have existed for the UV range to date due to the use of mercury. As the blue LED is now technologically very mature and available at low cost, we are pursuing an alternative approach to the stable emission of UV light that builds on the success of the phosphor-converted white LED. To this end, we are using the concept of two-photon upconversion, which generates a higher-energy UV photon from two blue photons. A suitable emitter for this is the 4f² ion Pr³⁺, which has excited states of the 4f¹5d¹ configuration in the UV range. So far, however, this process is still surprisingly inefficient. Through targeted design strategies in the chemistry and structure of the host compounds, we would like to gain a better understanding of the crucial loss channels and thus develop design strategies for implementing this upconversion process in an energy-efficient and cost-effective manner. In this way, we hope to use lanthanide ions to create promising new and efficient UV light sources in the future, using technology already established in the lighting industry.