Triplet-triplet annihilation(TTA) upconversion is a technique converting low energy photos into high energy photos by a multi photon mechanism.The TTA based upconversion has a broad application prospect in solar cells
photocatalytic
anti counterfeiting and bioimaging
etc.The traditional TTA based upconversion mainly occurs in anaerobic solution
which may significantly limit its applications.Recently
the development of TTA upconversion in solid state has attracted much attention.And the development over the past ten years of solid state TTA upconversion in polymer matrix from the state of polymer and the dispersion mode of TTA system is summarized in this review.