  Artificial lighting is a widespread technology which consumes large amounts
of energy. Triplet-triplet annihilation photochemical upconversion is a method
of converting light to a higher frequency. Here, we show theoretically that
photochemical upconversion can be applied to Watt-scale lighting, with
performance closely approaching the 50% quantum yield upper limit. We describe
the dynamic equilibrium of an efficient device consisting of an LED, an
upconverting material, and an optical cavity from optical and thermal
perspectives.
