Photon Upconversion through a Cascade Process of Two-Photon Absorption in CsPbBr₃ and Triplet–Triplet Annihilation in Porphyrin/Diphenylanthracene

Photon upconversion constitutes an exceptionally rich area of research in photonics and electronics, where low-energy light is converted to high-energy light through nonlinear processes represented by two-photon absorption (TPA) and triplet–triplet annihilation (TTA). Here, we report a cascade process of TPA in inorganic perovskite quantum dots (PQDs) of CsPbBr₃ and TTA in an organic molecule (9,10-diphenylanthracene) mediated by an octaethylporphyrinatoplatinum­(II) (PtOEP) sensitizer. This sequential energy transfer enables upconversion from four photons from a near-infrared femtosecond laser at 800 nm to one photon at 430 nm with a large anti-Stokes shift of ∼1.3 eV. We characterize the energy transfer from PQDs to PtOEP by picosecond lifetime spectroscopy and a Stern–Volmer plot of the steady-state photoluminescence while considering dynamic and static quenching as well as trivial absorption and Förster (fluorescence) resonance energy transfer. The serial connection of TPA and TTA achieved in a simple system opens up an attractive avenue in nonlinear photonics and harvesting of low-energy photons.