Design and Characterization of Novel Porphyrins with Oligo(phenylethylnyl) Links of Varied Length for Dye-Sensitized Solar Cells: Synthesis and Optical, Electrochemical, and Photovoltaic Investigation

Abstract

Novel zinc porphyrins with 1-4 π-conjugated phenylethylnyl (PE) units (labeled PE1-PE4) as a link of controlled length were synthesized for fundamental tests and applications as a dye-sensitized solar cell (DSSC). The UV-visible spectra of the solution samples show clear absorption patterns of the PE groups in a region 300-400 nm, consistent with results calculated with density-functional theory. Cyclic voltammograms of PE1-PE4 in tetrahydrofuran show similar electrochemical potentials for each compound. Femtosecond fluorescence up-conversion of solution samples and of porphyrin-sensitized TiO 2 films was measured with excitation at 420 or 430 nm and emission at 460, 470, 620, and 680 nm. When these porphyrins were fabricated into DSSC devices, the efficiency of power conversion of these devices decreased systematically with increasing length of the link: 2.5 ( 0.2% (PE1), 2.0 ( 0.1% (PE2), 0.78 ( 0.09% (PE3), 0.25 ( 0.02% (PE4). This great photovoltaic degradation from PE1 to PE4 is not interpretable according to the rate of electron injection independent of length; other factors, including electron transfer from the semiconductor back to the porphyrin cation or the electrolyte, must be considered to account for the observed dependence of photovoltaic performance on length.

Enhanced performance of ruthenium dye-sensitized solar cell by employing an organic co-adsorbent of N , N ’-bis((pyridin-2-yl)(methyl) methylene)- o -phenylenediamine

“…Hence, the photon lost due to the light absorption by I 3 À will be suppressed by employing BPPI as a co-adsorbent due to the competition between BPPI and I 3 À to absorb light. When absorbed on TiO 2 film, the absorption of N719 is remarkably broadened due to the electronic coupling of the dyes on the TiO 2 surface [25]. After co-adsorption with BPPI, its absorption was enhanced in the region of 300-700 nm, especially around 400 nm where BPPI could compensate for that of N719.…”

Zinc–Porphyrin Dyes with Different meso‐Aryl Substituents for Dye‐Sensitized Solar Cells: Experimental and Theoretical Studies

“…Furthermore, its inherent LUMO level is situated above the conduction band of TiO 2 , and its HOMO level is below the redox couple of the electrolyte solution required for charge separation at the semiconductor-dye-electrolyte surface, which makes it a good donor moiety. [9] So far, a large number of porphyrins have been developed as sensitizers for DSSCs such as carboxyphenyl metalloporphyrins (h = 0.2-3.6 %); [10] thiophene-, olefin-, and acetylene-linked porphyrins (h = 3.6-5.1 %); [11] quinoxaline-fused porphyrins (h = 5.2-6.5 %); [12] zinc-zinc porphyrin dimers (h = 2.1-5.5 %); [13] bacteriochlorin (h = 1.1-6.6 %); [14] 2,4-pentadienoic acid bpyrrolic-functionalized porphyrins (h = 3.03-7.47 %); [15] phenylethynyl-substituted porphyrins (h = 0.25-6.12 %); [16] meso-(diarylamino)-substituted porphyrins (h = 3.8-13 %); [7,17] 4-ethynylstyryl b-pyrrolic-functionalized porphyrins (h = 4.3-7.1 %); [18] and acene-modified porphyrins (h = 0.10-5.44 %). [19] The performances of these porphyrins varied depending on the chemical structure.…”

Cation Exchange at Semiconducting Oxide Surfaces: Origin of Light-Induced Performance Increases in Porphyrin Dye-Sensitized Solar Cells

“…7,9 Their synthesis is relatively straightforward, and their optical and electronic properties can be easily tuned via chemical modification of the porphyrin core, 10 the number of porphyrin units, 11,12 and the linker between the core and the inorganic oxide. 13 The capability of porphyrin sensitizers was recently highlighted by a report demonstrating a new DSSC benchmark efficiency of 12.3 % under AM 1.5 full sunlight for a device with a donor-π-acceptor zinc porphyrin sensitizer coupled with a cobalt-based redox mediator. 7 This report demonstrated the remarkable potential of this class of chromophores, although the majority of porphyrin dyes have not approached such impressive efficiencies despite major progress in the development of innovative design strategies.…”