Characteristics of Dye-Sensitized Solar Cells with TiO2 Stripes.

A TiO2 strip array with a thickness of 90 nm was fabricated by photolithography and physical vapor deposition. This work utilized the chemical and physical methods to fabricate the TiO2 strip array. A porous semiconductor layer made of TiO2 nanoparticles was coated on the TiO2 strip array. The TiO2 strip array has a one-dimensional protrusive structure. The energy conversion efficiency (4.38%) of a dye-sensitized solar cell (DSSC) with the TiO2 strip array exceeded that (3.20%) of a DSSC without a TiO2 strip array by 37%. In addition, this result was verified by the electrochemical impedance spectra of the two DSSCs. Therefore, the TiO2 strip array can be used to increase the energy conversion efficiencies of DSSCs. The large energy conversion efficiency of the DSSC with the TiO2 strip array arises from the large surface area of the one-dimensional protrusive structure and its specific electron transport paths. The DSSC with the TiO2 strip array has advantages of economical production cost, easy fabrication, and boosting energy conversion efficiency.

An investigation of organic photovoltaics improvement via extension of the exciton lifetime.

The phosphorescent material tris(phenylpyrazole)iridium (Ir(ppz)3) was doped into the bulk heterojunction (BHJ) layer of a 3-hexylthiophene-2,5-diyl and indene-C60 bisadduct blend to form more excitons in the triplet state. Triplet-state excitons have longer lifetimes than singlet-state excitons. Surface phase separation was determined via atomic force microscopy and the vertical distribution of various molecules was analyzed via secondary ion mass spectroscopy. Several annealing processes were applied to the BHJ layer doped with Ir(ppz)3 to investigate the thermal stability of the film. The exciton lifetime in the BHJ film was characterized using femtosecond time-reserved photoluminescence.