Synthesis of sterically hindered phthalocyanines and their applications to dye-sensitized solar cells

Abstract

Phthalocyanines with high peripheral substitutions and free from potential contamination by regioisomers have been synthesized and evaluated as photosensitizers for dye-sensitized solar cell applications. Each of the sterically hindered precursor compounds was accomplished by Suzuki-Miyaura cross-coupling reactions with the arylchloride and corresponding boronic acids. Metal free phthalocyanine-sensitized solar cells showed no photocurrent generation due to its low excited singlet state (LUMO) compared with the conduction band of TiO(2). Upon zinc metalation, the LUMO level of the phthalocyanine was pushed up, and this variation afforded an exergonic free energy change for electron injection. The zinc phthalocyanine-sensitized solar cell displayed 0.57% power conversion efficiency (eta) and 4.9% maximal IPCE in the near infrared region. More importantly, the cell prepared with and without the presence of chenodeoxycholic acid revealed no difference in the power conversion efficiency. This implies that the well-known aggregation tendency of phthalocyanines that is considered to enhance the self-quenching of the phthalocyanine excited singlet state is effectively suppressed by the high degree of substitutions. The significance of the driving force for electron injection and the distance between the dye core and the TiO(2) surface is also highlighted for devising high performance phthalocyanine photosensitizers.

Phenoxazine Dyes for Dye‐Sensitized Solar Cells: Relationship Between Molecular Structure and Electron Lifetime

“…With top efficiencies reaching 10 %, [7,8] the distance to the best inorganic dyes-with efficiencies of approximately 11 % [9,10] -should not be unreachable anymore. Many different kinds of chromophores have been examined in DSCs (such as porphyrin, [11,12] phthalocyanine, [13] indoline, [14,15] perylene, [16] triphenylamine (TPA), [7,8,[17][18][19][20][21][22] and hetero-anthracene) [23][24][25][26][27] and give efficiencies in the range of 5-11 %. Recently, TPA-based chromophores have gained great attention due to their potential as electron donors.…”

A Nonconjugated Bridge in Dimer-Sensitized Solar Cells Retards Charge Recombination without Decreasing Charge Injection Efficiency

“…Most previous attempts to decrease the charge recombination in DSSCs have therefore concentrated on insulating the TiO 2 with surface treatments, [10][11][12] small co-adsorber molecules, [13][14][15][16] or to add alkyl chains to sensitisers to prevent the approach of the electron acceptor species to the TiO 2 surface. [17][18][19][20] Recently, such strategies were incorporated into the design of a porphyrin sensitiser to produce a record power conversion efficiency of 12.1%. [21] Recently, dimer sensitisers have been paid attentions.…”

Molecular Engineering of Zinc Phthalocyanines with Phosphinic Acid Anchoring Groups

“…Phthalocyanines (Pcs) are promising sensitizers for molecular photovoltaics because of their intense red absorbance and their outstanding photochemical and thermal stability. [2][3][4] The goal of this study was to enhance the long-term photostability of DSSCs by molecularly engineering near-IR-absorbing dyes with anchoring groups that bind to the TiO 2 surface more strongly than the conventional carboxylic acid groups. [5] Herein, we report a phosphinic acid as an anchoring group for Pc-based sensitizers in DSSCs.…”