The goal of this research is to study the excited state dynamics of conjugated molecules, oligomers and polymers in the solid state and compare these photophysical properties to those found in solution. To study the triplet excited state dynamics of films a new nanosecond transient absorption instrumentation was developed. This instrument can detect transient absorption with ... A as low as of 10-3. Using this newly available instrumentation, it is possible to measure the triplet excited state dynamics so as to gain insight into several solid-state applications of photoactive molecules, oligomers, and polymers. A series of p-phenylene vinylene platinum acetylide complexes are studied for optical power limiting applications, and they are incorporated into poly(methyl methacrylate) (PMMA) monoliths. The photophysical properties of the monoliths and Triplet-triplet annihilation in conjugated co-polymers containing phenylene and p-phenylene vinylene platinum acetylide units is observed and compared against representative "monomer" complexes using transient absorption spectroscopy as a function of increasing laser fluence of the excitation pulse. The interaction between conjugated polymer, MEH-PPV, and a trimeric perfluoro-ortho-phenylene mercury complex, Hg3 is investigated in solution and in films. Finally cationic oligomers are intercalated into a clay host, and the photophysical properties of the clay-oligomer hybrid are investigated in disperse solutions and in films.