Monobenzoporphyrins as Sensitizers for Dye‐Sensitized Solar Cells: Observation of Significant Spacer‐Group Effect

Abstract

A series of monobenzoporphyrins (WH1-WH4) bearing different conjugated spacer groups were designed and synthesized as sensitizers for dye-sensitized solar cells. Although a phenyl spacer only has a minimal impact on the absorption bands of the monobenzoporphyrin, an ethynylphenyl (WH3) or a vinyl (WH4) spacer redshifts and broadens the absorption bands of the dyes to result in much enhanced light-harvesting ability. Dye-sensitized solar cells based on these monobenzoporphyrin dyes displayed remarkable differences in power conversion efficiencies (PCEs). The monobenzoporphyrin bearing no spacer (WH1) resulted in a PCE of only 0.5 %; in contrast, the monobenzoporphyrin bearing vinyl spacers (WH4) achieved a PCE of 5.2 %. The high efficiency of the WH4 cell is attributed to the higher light-harvesting ability, the lesser extent of aggregation on the TiO2 surface, and the more favorable electron-density distributions of the HOMO and LUMO for electron injection and collection. This work demonstrates the exceptional tunability of benzoporphyrins as sensitizers for dye-sensitized solar cells.

β‐Functionalized Push–Pull opp‐Dibenzoporphyrins as Sensitizers for Dye‐Sensitized Solar Cells

“…Herein, we present the synthesis, characterization, and evaluation of a series of β‐functionalized push–pull opp ‐dibenzoporphyrins as sensitizers in DSSCs (Figure ). In a previous publication, we showed that a monobenzoporphyrin bearing vicinal acrylic acid anchoring groups displayed a high power conversion efficiency ( η ) of 5.24 %, which is close to that of the N3 cell obtained under similar conditions ( η =6.92 %). In this work, a push–pull opp ‐dibenzoporphyrin bearing anchoring groups similar to those of monobenzoporphyrin ( WH4 ) displayed a much higher power conversion efficiency ( η =5.9 %) than WH4 ( η =4.81 %) under similar conditions.…”

“…It was reported that slight modification of the donor and/or the acceptor group(s) could make a significant difference in the power conversion efficiency . Our previous work and work from other groups also suggested that different spacer groups between the anchoring group (carboxylic acid group) and the porphyrin core could also bring about significant changes to the power conversion efficiency . It would be interesting to learn what factors determine the power conversion efficiency of these β‐functionalized opp ‐dibenzoporphyrins.…”

“…The synthesis of push–pull dibenzoporphyrins YH1 – YH3 is illustrated in Scheme . The starting material, 2,3‐dibromoporphyin ( 1 ), was prepared by using a previously published two‐step procedure . One benzene ring was then fused at the porphyrin β,β′‐positions through a Pd 0 ‐catalyzed cascade reaction to give monobenzoporphyrins 2 a and 2 b bearing vicinal phenyl groups and p ‐methoxyphenyl groups, respectively.…”

“…Subsequent 6π‐electrocyclization and aromatization followed by zinc insertion led to Zn‐ 5 c , which was then converted into final push–pull opp ‐dibenzoporphyrin YH3 through hydrolysis. For comparison purposes, monobenzoporphyrin WH4 was also prepared by following a reported procedure …”

Competitive Energy and Electron Transfer in β‐Functionalized Free‐Base Porphyrin–Zinc Porphyrin Dimer Axially Coordinated to C60: Synthesis, Supramolecular Formation and Excited‐State Processes

“…The synthesis of porphyrin monomer and dimer is illustrated in Scheme . The starting compound, 2,3‐dibromoporphyrin 1 was synthesized using published two‐step procedure ,. Then one benzene ring was fused at the porphyrin β, β′‐position by Pd 0 ‐catalyzed Heck reaction followed by one‐pot cyclization and aromatization to give monobenzoporphyrin 2 ,.…”