Naphthyl-Fused π-Elongated Porphyrins for Dye-Sensitized TiO₂ Cells

Abstract

Novel unsymmetrically π-elongated porphyrins, in which the naphthyl moiety is fused to the porphyrin core at the naphthyl bridge with a carboxyl group (fused-Zn-1) or at the opposite side of the phenyl bridge with a carboxyl group (fused-Zn-2), have been synthesized to improve the light-harvesting abilities in porphyrinsensitized solar cells. As the results of π-elongation with low symmetry, Soret and Q bands of fused-Zn-1 and fused-Zn-2 were red-shifted and broadened, and the intensity of Q-band relative to that of Soret band was enhanced. The fused-Zn-1 and fused-Zn-2-sensitized TiO 2 solar cells showed the power conversion efficiencies (η) of 4.1% and 1.1%, respectively, under standard AM 1.5 conditions. The η value of the fused-Zn-1 cell was improved by 50% compared to the reference cell using unfused porphyrin (Zn-1). The fused-Zn-1-sensitized cell revealed high IPCE (incident photon-to-current efficiency) values of up to 55%, extending the response of photocurrent generation close to 800 nm. Thus, the improved photocurrent generation of the fused-Zn-1-sensitized cell relative to the Zn-1-sensitized reference cell is responsible for the remarkable difference in the η values. The η value of the fused-Zn-2 cell was much lower than that of the fused-Zn-1 cell. DFT calculations disclosed that there are significant electron densities on the carboxyl group in the LUMO of fused-Zn-1, whereas there are little electron densities on the carboxyl group in the LUMO of fused-Zn-2. Accordingly, the larger electronic coupling between the porphyrin and the TiO 2 surface in the fused-Zn-1-sensitized cell may be responsible for the high cell performance, due to the efficient electron injection from the porphyrin excited singlet state to the conduction band of the TiO 2 electrodes. To further improve the cell performance, 5-(4-carboxylphenyl)-10,15,20-tetrakis-(2,4,6-trimethylphenyl)porphyrinatozinc(II) (Zn-3), possessing different light-harvesting properties, was coadsorbed with fused-Zn-1 onto an TiO 2 electrode. Under the optimized conditions, the cosensitized cell yielded maximal IPCE value of 86%, short circuit photocurrent density of 11.7 mA cm -2 , open-circuit voltage of 0.67 V, fill factor of 0.64, and η of 5.0% under standard AM 1.5 conditions.

Conformational Effects on the Dynamics of Internal Conversion in Boron Dipyrromethene Dyes in Solution

“…Indeed, such strategies may have relevance to the design of dye-sensitized solar cells [5] and certain organic light-emitting diodes.…”

A Cyclic Porphyrin Tetramer Linked by Azo and Butadiyne Bridges

“…The fact that porphyrin derivatives are part of light harvesting and photo-induced electron transfer systems in the photosynthetic apparatus of plants suggests that porphyrins could be used as photosensitisers in dye-sensitized solar cells. [13,[66][67][68][69] However, individual porphyrin units exhibit relatively narrow absorption bands which results in low power conversion efficiencies when porphyrin-containing polymers are used as active layers in organic solar cells. [68,70] Thus, a polymer incorporating larger porphyrinic arrays such as that found in compound 1 might exhibit a greater efficiency.…”

Synthesis and properties of meso-arylporphyrin – closo-decaborate anion conjugates

“…One of the strategies to increase DSSC efficiency is to extend the absorption spectra of the sensitizer (in order to maximize the overlap with solar spectrum) and its shift to the red region, which can be achieved by increasing the coupling in the system [10,11] or selection of appropriate donor group. [12][13][14][15] Not less important characteristic of the DCCS is resistance to photochemical degradation.…”

“…[16] In this work new donor-acceptor conjugates based on aminoporphyrins and boron cluster [B 10 H 10 ] 2-were received by reaction of nucleophilic addition. In this reaction porphyrin amino group reacts with nitrilium derivative of closo-decaborate anion [2-B 10 H 9 N≡CMe] -.…”