Advanced Cd^II complexes as high efficiency co-sensitizers for enhanced dye-sensitized solar cell performance

Abstract

This work reports on two new complexes with the general formula [Cd3(IBA)3(Cl)2(HCOO)(H2O)]n (1) and {[Cd1.5(IBA)3(H2O)6]·3.5H2O}n (2), which can be synthesized by the reaction of Cd(II) with rigid linear ligand 4-HIBA containing imidazolyl and carboxylate functional groups [4-HIBA = 4-(1H-imidazol-1-yl)benzoic acid]. Single-crystal X-ray diffraction analyses indicate that complex 1 is a 2D "wave-like" layer structure constructed from trinuclear units and complex 2 is just a mononuclear structure. Surprisingly, both complexes 1 and 2 appear as a 3D supramolecular network via intermolecular hydrogen bonding interactions. What's more, due to their strong UV-visible absorption, 1 and 2 can be employed as co-sensitizers in combination with N719 to enhance dye-sensitized solar cell (DSSC) performance. Both of them could overcome the deficiency of the ruthenium complex N719 absorption in the region of ultraviolet and blue-violet, and the charge collection efficiency is also improved when 1 and 2 are used as co-sensitizers, which are all in favor of enhancing the performance. The DSSC devices using co-sensitizers of 1/N719 and 2/N719 show an overall conversion efficiency of 8.27% and 7.73% with a short circuit current density of 17.48 mA cm(-2) and 17.39 mA cm(-2), and an open circuit voltage of 0.75 V and 0.74 V, respectively. The overall conversion efficiency is 27.23% and 18.92% higher than that of a device solely sensitized by N719 (6.50%). Consequently, the prepared complexes are high efficiency co-sensitizers for enhancing the performance of N719 sensitized solar cells.

Heterodimetallic Ferrocenyl Dithiophosphonate Complexes of Nickel(II), Zinc(II) and Cadmium(II) as Sensitizers for TiO2‐Based Dye‐Sensitized Solar Cells

“…From Table the HOMO values for Ni(II), Zn(II), and Cd(II) complexes were calculated to be −4.75, −4.93, −4.79 and −4.83 eV, while the LUMO levels were calculated to be −2.90, −2.93, −2.54 and −2.68 eV using equations 1 and 2 . The LUMO level of a sensitizer should be above the conduction band (CB) of the TiO 2 semiconductor (−4.40 eV vs. vacuum) for efficient electron injection, while the HOMO energy level should stay below the energy level of the I − /I 3 − redox couple (−4.85 eV vs. vacuum) for regeneration .…”

“…To further determine electron transport time (τ d ) which is a measure of the rate of an electron injected to the collecting electrode, the electron lifetime was estimated from the peak frequency of the Bode phase plots. The τ d values were calculated using the expression adopted from Gao, et al . shown in Eq.…”

“…Since Grätzel and O′Regan reported the first dye‐sensitized solar cells (DSSCs), the result has drawn attention due to the high photon‐to‐electricity conversion efficiency, ease of fabrication, and low production cost involved . As a result, investigations into metal complexes for photovoltaic applications have seen an increase . A major obstacle in refining the efficiency of photovoltaic energy conversion concerns the spectral incompatibility between the energy distribution of photons in the incident solar spectrum and the bandgap of a chosen semiconductor material …”

“…Co‐sensitization is an effective approach to advance the device performance through a combination of two or more dyes sensitized by the same semiconductor film and thus extending the light harvesting spectrum . With the aim of finding efficient sensitizers, many new commercial and synthetic dyes have been investigated for spectral sensitization of wide‐bandgap semiconductor electrodes.…”

A Visible-NIR Responsive Dye-Sensitized Solar Cell Based on Diatom Frustules and Cosensitization of Photopigments from Diatom and Purple Bacteria

“…erefore, more interests are focused on exploring the nearinfrared absorbance dyes or spectral complementary cosensitization dyes, such as synthesized FT89 NIR dye enhanced photocurrent conversion efficiency by 6% compared to N749 benchmark [12]; bacteriochlorophyll c (BChl c) from green sulfur bacterium showed a photocurrent conversion efficiency of 0.1% at 600-800 nm [13]. Cosensitizers (N719, black dye, SQ1, NI5, and porphyrin) could enhance the photoelectric performance of DSSC [14][15][16]. However, few studies focus on natural NIR dye or cosensitized natural NIR dye.…”