Sandwich‐Type Porphyrin Complexes as Efficient Sensitizers for Triplet‐Triplet Annihilation Upconversion

Abstract Two sandwich‐type porphyrin complexes Pd(MeTPP) 2 and Pt(MeTPP) 2 have been synthesized by the longitudinal coordination of metal ion and porphyrin. The sandwich‐type porphyrin complexes present long triplet lifetime, which is almost 1.4 times longer than the single‐decker porphyrin complexes. Their long triplet lifetimes result in high upconversion quantum yields. An increasing upconversion quantum yield (Φ UC ) of up to 29.1 % is obtained under excitation of low power density at 78 mW cm −2 . Moreover, porphyrin complexes are used in photoelectrochemical cell to realize sub‐bandgap photo capture and conversion. It is manifested that sandwich‐type structure provides an effective method for porphyrin complexes to enhance the upconversion quantum yield.