Fluid-processed tetraazaporphyrin-based photovoltaics

AEI 69

Brian D. Pate, Brian.Pate@wpafb.af.mil1, Joy E. Rogers2, Barney E. Taylor1, Britt A. Minch3, James R. Deneault1, Adam P. Smith1, and Michael F. Durstock3. (1) Air Force Research Laboratory, Universal Technology Corporation, Materials & Manufacturing Directorate, AFRL/MLBP, 2941 Hobson Way, B654-R304, Wright-Patterson AFB, OH 45433, (2) UES, Inc, (3) Air Force Research Laboratory
Photovoltaic (PV) cells with active bilayers composed of vapor-deposited copper phthalocyanine and C60-fullerene exhibit photoconversion efficiencies approaching 5%, making them among the most efficient PV cells based on small molecule heterojunctions. In order to increase this figure and enable more flexible, inexpensive processing of novel device architectures, fluid-based processing routes are desirable. In particular, we have examined the directed assembly of fluid-processable tetraazaporphyrin derivatives, including phthalocyanines, within PV devices, and have characterized a wide range of photoconversion efficiencies depending on the choice of central metal and peripheral substituents, as well as the processing conditions and resultant active layer morphology. Correlations have been established between triplet electronic excited state lifetimes, as observed by laser flash photolysis, and these device results. These trends point to the particular importance of both molecular and aggregate electronic structure in determining device performance.