Photoelectrochemical Behavior of Polychelate Porphyrin Chromophores and Titanium Dioxide Nanotube Arrays for Dye-Sensitized Solar Cells

Abstract

The influence of TiO2 nanotube array (NTA) morphology on dye-sensitized solar cell performance was studied with five porphyrin chromophores containing up to four carboxylic acid anchor groups. The TiO2 NTAs were anodically grown on Ti foil in NH4F electrolyte containing additives such as poly(ethylene glycol) (PEG 400), ethylene glycol, and glycerol. The NTAs grown in the presence of PEG 400 had the largest nanotube diameter (∼120 nm) and also yielded the best photoresponse with all five porphyrins in iodide/polyiodide electrolyte. Interestingly, nanoporous TiO2 “control” films, anodically grown on Ti foil in the absence of the organic additive, yielded an inferior photoresponse under the same conditions. Two of the porphyrins (P3 and P5), envisioned to have a spider-like configuration on the TiO2 NTA surface, yielded the best photoresponse among the five candidates in the Q(1,0) porphyrin spectral region. This result underlines that the molecular structure of the chromophore affects the directionality of electron transfer and its consequent ability to inject electrons (by the photoexcited porphyrin) into the oxide nanotube host. Finally, some perspectives on the use of TiO2 NTAs and porphyrins in DSSCs are given against the backdrop of the above data.

Enhancement of p-Type Dye-Sensitized Solar Cell Performance by Supramolecular Assembly of Electron Donor and Acceptor

“…The LUMO levels of TCPP and ZnTCPP are −0.9 V24 and −1.1 V34 vs. NHE , which are above the energy level of C60PPy •− as well as redox couples. Therefore, the porphyrin dye regeneration by C60PPy •− or redox couples are both thermodynamically feasible.…”

“…The HOMO levels of TCPP and ZnTCPP are 1.01 V24 and 0.96 V34 vs. NHE , respectively, well below the energy level of E VB of NiO; this indicates that hole injection from dye into VB of NiO is thermodynamically feasible. The LUMO levels of TCPP and ZnTCPP are −0.9 V24 and −1.1 V34 vs. NHE , which are above the energy level of C60PPy •− as well as redox couples.…”

Electrodeposition of Semiconductors

“…The TiO 2 NTAs anodically prepared as discussed above have been deployed for hydrogen sensing [189][190][191][192][193][194], solar or UV-assisted water photoelectrolysis [187,[195][196][197][198][199], electrocatalytic methanol oxidation [200], dye-sensitized solar photovoltaic cells [197,[201][202][203][204][205][206], and heterogeneous photocatalytic remediation of environmental pollutants [207].…”

Synthesis of a hybrid assembly composed of titanium dioxide nanoparticles and thin multi-walled carbon nanotubes using “click chemistry”

“…Titanium dioxide (TiO 2 ) nanoparticles are considered to be among the best photocatalytic materials due to their long-term thermodynamic stability, strong oxidizing power, and relative nontoxicity [5,6]. They have also recently been utilized in many applications such as gas sensing, photochromic devices, and solar cells [7,8]. To date, a variety of strategies have been employed to assemble TiO 2 nanoparticles with carbon nanotubes, including sol-gel processes, electrophoresis, hydrothermal hydrolysis, chemical vapor deposition (CVD), and physical vapor deposition (PVD) [9][10][11].…”