Organic Photovoltaics Using Tetraphenylbenzoporphyrin Complexes as Donor Layers

High efficiency, small molecule organic solar cells using platinum tetraphenylbenzoporphyrin (PtTPBP) (metal-TPBP) as the donor layer was demonstrated. Photovoltaic cells were grown on solvent-cleaned 150nm indium tin oxide (ITO)-coated glass substrates. Both Pt and Pd tetraphenylbenzoporphyrin were synthesized, and purified by vacuum thermal gradient sublimation. The organic materials, copper phthalocyanine (CuPc), fullerene (C60), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) were also purified by sublimation with one (C60) or two (CuPc and BCP) cycles before use. Thin films of the donor layer were spin-coated from 1mL of a toluene solution of PtTPBP, at 1500 rpm for 40 s to obtain a 150 Å thick layer onto previously cleaned ITO. The thickness was measured by ellipsometry and UV-vis absorption spectroscopy. The emission spectrum of a PtTPBP film shows a broad, featureless band that is significantly red-shifted relative to the solution.