Triplet Exciton Diffusion in Platinum Polyyne Films

A time-resolved photoluminescence quenching approach is developed for determining the triplet exciton diffusion coefficient and diffusion length (D and L-D, respectively) of phosphorescent conjugated polymers. This method is applied to a solid-state organometallic conjugated polymer with the structure [-Pt(PBu3)(2)CCC6H4CC-]n (where Bu = n-butyl and -C6H4 is 1,4-phenylene). The approach relies on analysis of the lifetime quenching of the polymers phosphorescence by a series of three different quenchers that are dispersed into the polymer phase at varying concentration. The lifetime quenching data are analyzed by using a modified SternVolmer quenching expression to determine the diffusion-controlled quenching rate constant, kq, which is then related to the exciton diffusivity, D, and diffusion length, LD. The diffusion coefficients that are determined using the three quenchers are consistent, D approximate to 4 x 106 cm2 s1, and combined with the triplet exciton lifetime of the pristine polymer (t = 1.05 mu s) give an exciton diffusion length L-D approximate to 22 nm. The results are compared to literature studies of singlet exciton diffusion in conjugated polymers and triplet exciton diffusion in molecular materials.