Across the Interface: Understanding the Mechanism of Perovskite-Sensitized Triplet–Triplet Annihilation

Perovskite-sensitized photon upconversion may provide a viable solution toward developing efficient solid-state upconversion systems due to favorable photophysical properties such as long carrier lifetimes and compositional tunability in the perovskite. This method of photon upconversion differs from the extensively explored solution-based upconversion systems due to free carrier generation within bulk perovskites, which results in triplet generation by charge injection rather than bound triplet exciton transfer. In addition to differing sensitizer charge generation mechanisms, generated triplets must diffuse within the solid state prior to successful upconversion, introducing another layer of complexity. To this end, we outline the current mechanistic understanding of the perovskite-based triplet sensitization process and discuss the future directions of the field and the viability of future technological implementation.