Function of Tetrabutylammonium on High-Efficiency Ruthenium Sensitizers for Both Outdoor and Indoor DSC Application

Abstract

The function of tetrabutyl ammonium ions (TBA + ) in a sensitizer used in dye-sensitized solar cells (DSC) is contradictory. TBA + can reduce unwanted charge-recombination by protecting the TiO 2 surface and reduce dye aggregation, enhancing the photovoltaic performance. It will also compete with the dye-loading on the TiO 2 film, decreasing the short-circuit current density of the cell. Three ruthenium sensitizers (DYE III, DUY11, and DUY12 containing two H + , one H + /one TBA + , and two TBA + , respectively) were prepared to systematically investigate the function of TBA + in a dye for DSC under both standard sunlight and indoor illumination. The optical properties and frontier orbital energy level of the sensitizers are not influenced significantly by the number of TBA + . Under the standard 1 sun illumination, DSCs based on DUY11 (containing one H + and one TBA + ) achieved the highest power conversion efficiency (PCE) of 11.47%. Overall, optimized DSCs sensitized by the three ruthenium dyes all have the PCE over 10%, which is higher than that (9.95%) of N719-dyed cell fabricated at the same conditions. Under the illumination of a light emitting diode (LED), DSCs sensitized by DUY11 also have the highest efficiency of 19%. Furthermore, DUY12 with two TBA + exhibits superior photovoltaic performance compared to a DYE III (containing two H + in the anchoring ligands)-dyed cell; although these two dyes have similar photovoltaic performance under standard 1 sun lighting. The important function of TBA + in reducing the charge recombination (by protecting TiO 2 surface and avoiding dye aggregation) of a DSC under indoor lighting (when small number of electrons were excited by weak light) is also revealed.

Steric Effects on the Photovoltaic Performance of Panchromatic Ruthenium Sensitizers for Dye-Sensitized Solar Cells

“…The heteroleptic Ru complex was prepared with the one-pot reaction protocol similar to our previous report . 0.337 g (0.55 mmol) of [RuCl 2 ( p -cymene)] 2 and 0.736 g (1.10 mmol) of ancillary ligand bearing two 2-thiohexyl-3,4-ethylenedioxy-thiophene (TH-EDOT) units (L20) were prepared according to the literature; 0.692 g (1.10 mmol) of L22-ester and excess ammonium thiocyanate (NH 4 NCS) were added in a Schlenk flask containing DMF and then hydrolyzed with 0.115 g (2.75 mmol) LiOH·H 2 O in water. After refluxing for 12 h, dilute HNO 3(aq.)…”

“…It is shown that the device sensitized with CYC-B22 displays a panchromatic response extending to 850 nm, which is broader than those of the cells based on CYC-B23C, CYC-B23T, N719, and the other bipyridyl heteroleptic Ru complexes using dcbpy anchoring ligand. 1,2,15,16,[30][31][32][33][34][35][36]47 Evidently, the highest J sc and PCE of CYC-B22-sensitized device are ascribed to the best light-harvesting capability provided by the highly conjugated anchoring and ancillary ligands as well as the highest amount of dye-loading (77.8 nmol cm −2 in Table 2) for the largest light-harvesting efficiency 17 (LHE; Figure S7). Surprisingly, the PCE of the CYC-B23T-sensitized device is comparable with that of the CYC-B22-based cell but remarkably higher than those of cells dyed with its stereoisomer (CYC-B23C).…”

Ruthenium‐based complex dyes for dye‐sensitized solar cells

“…Using TBA + to replace H + has the advantages of increasing the solubility of the sensitizer, at the same time, to avoid the protonation of TiO 2 to lower its Fermi level and therefore to reduce the theoretic open-circuit voltage (V OC ) when the dye molecules adsorbed on TiO 2 anode. [9] Z-907 dye [10] (its structure see Figure 1) is also a representative [2211] ruthenium dye reported by Grätzel et al They used two hydrophobic nonyl groups to replace two carbonylate groups in one of the bidentate anchoring ligand of N3 dye to increase the hydrophobility of the dye molecules. The PCE of Z-907 dyed DSC is only 6.6%, nevertheless, DSC based on Z907 dye reveals good longterm stability.…”

Challenges and prospects of ambient hybrid solar cell applications

“…Nguyen et al studied a Ru dye and the effect that tetrabutylammonium cations (as a salt on the COO − anchoring group before attachment on titania) have on cell efficiency when they replace the protons of the carboxylic groups. 45 The larger cation, in fact, can help to protect the TiO 2 surface and reduce dye aggregation, but at the same time it will reduce dye loading. They found that adding a single tetrabutylammonium cation to the dye gives the best results, with device efficiencies varying between 14% at 363 lx and 32% at 6372 lx.…”