On the potential of porphyrin-spiked triarylamine stars for bulk heterojunction solar cells

A novel porphyrin-triarylamine compound was synthesized to serve as a photosensitizer in bulk heterojunction solar cells (BHJ-OSCs). Based on cyclic voltammetric analysis, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the target porphyrin trimer were determined to be at -5.4 and -3.5 eV versus vacuum, respectively, and compared with those of other materials used for the construction of the BHJ-OSCs. Absorption and emission spectra of the film of the target porphyrin trimer were in good agreement with those of its solution. The charge transfer in a blended film of the porphyrin-triarylamine compound with phenyl-C-61-butyric acid methyl ester (PCBM) was proven possible by photoluminescence measurements. The energy conversion efficiency of the BHJ-OSCs based on the target compound depended strongly on the donor : acceptor weight ratio and the thickness of the organic layer. Surface nanomorphologies of the films with different donor : acceptor ratios and thickness were investigated by atomic force microscopy (AFM). The short circuit current density (J(SC)) up to 2.06 mA cm(-2) was obtained from the BHJ-OSC fabricated herein.