Hybrid bulk heterojunction solar cells fabricated by TiO2 aerogel and porphyrins

Hybrid bulk heterojunctions provide a technically and economically credible alternative to conventional silicon based photovoltaic technologies. New hybrid bulk heterojunction solar cells fabricated with a TiO2 aerogel and a series of porphyrins have been studied in this work. The porphyrins act as the sunlight absorber, electron donor, and hole-transporter, while the TiO2 aerogel is the electron acceptor and electron-transporter. The porphyrins are tetraphenylporphyrins with para substituted groups: stilbene branches, hydroxyl and p-methoxyl groups. The films were characterized by AFM and UV-Visible spectroscopy. Photoelectrical characterization was conducted by 2-probe J-V measurements. Highly transparent TiO2 nanostructured films with transmission in excess of 90% and nanocrystals of about 11 nm in diameter were prepared. The conversion efficiency of the devices was observed to be highly dependent on the hydrophilicity of the porphyrins. Best conversion efficiency for these devices was greater than 0.4%.