Iodine-Pseudohalogen Ionic Liquid-Based Electrolytes for Quasi-Solid-State Dye-Sensitized Solar Cells

Abstract

In the current work, novel symmetrically alkyl-substituted imidazolium-based ionic liquids have been synthesized featuring either iodide (I) or selenocyanate (SeCN) as counteranions. Physicochemical assays based on spectroscopy and electrochemistry techniques have been performed to identify the best ionic liquid for application as electrolytes in quasi-solid-state dye-sensitized solar cells (qssDSSC). The latter were mixed with additives such as 4-tert-butylpyridine (4tbpy) and guanidinium thiocyanate (GuSCN) to optimize electrode surface coverage, ionic diffusion, and dye regeneration. In addition, we demonstrate that electrolytes containing a mixture of I and (SeCN) enhance the open-circuit voltage of the final quasi-solid-state device by up to 70 mV. As such, iodine-pseudohalogen electrolytes reveal in qssDSSCs a good balance between dye regeneration and hole transport and, in turn, enhance the overall solar energy conversion efficiency by 70% with respect to reference qssDSSCs with iodine-based electrolytes. Finally, devices with the iodine-pseudohalogen electrolyte show a 1000 h stable efficiency of 7-8% under outdoor temperature operation conditions and 1 sun illumination.

NMR Spectroscopic Studies of Cation Dynamics in Symmetrically-Substituted Imidazolium-Based Ionic Liquid Crystals

“…where P 2 (cos θ NL ) = (3 cos 2 θ NL − 1)/2 and θ NL = 90 • is the angle between the director and the magnetic field vector. Any possible contribution from the biaxiality term (see below) is neglected in Equation (2). The accepted values for the dipolar coupling constants in the principal frame b CH = −(µ 0 /8π 2 )(γ H γ C /r 3 CH ), with account for vibration effects, are −21.5 kHz and −22 kHz for aliphatic and aromatic sites, respectively [34,35].…”

“…NL    is the angle between the director and the magnetic field vector. Any possible contribution from the biaxiality term (see below) is neglected in Equation (2). The accepted values for the dipolar coupling constants in the principal frame…”

“…It is anticipated that these non-molecular compounds are going to have a strong impact on the future development of functional materials for a variety of applications. For example, ILC-based devices for low-dimensional transport of ions and electrons hold great potential for applications in electrochemistry [2,3]. ILCs have already been used as templates to synthesize mesostructured porous materials [4][5][6] and as orientationally-ordered ionic solvents in catalysis [7,8].…”

Recent advances in eco-friendly and cost-effective materials towards sustainable dye-sensitized solar cells

“…Pseudohalogens are among the first alternative redox couples reported in the literature. 215,216 In particular, the SeCN − /(SeCN) 2 couple can be easily incorporated in a photo-reticulated polymer membrane, which may potentially enhance the long-term stability of devices (i.e. the trapping of the redox couple in a polymer matrix greatly reduces the evaporation of the electrolyte solvent), thus representing a step forward towards their commercialization.…”

An efficient and thermally stable dye-sensitized solar cell based on a lamellar nanostructured thiolate/disulfide liquid crystal electrolyte and carbon/PEDOT composite nanoparticle electrode

“…5 However, due to the shortcomings of the I À /I 3 À redox couple such as corrosion of the metal CE and absorption of visible light, many attempts have been invested to nd alternative redox couples to replace the ubiquitous I À /I 3 À system. [6][7][8][9] An organic thiolate/disulde (T À /T 2 ) redox couples with noncorrosive and transparent nature, as well as acceptable efficiency have drawn attention as promising alternative mediators for DSSC applications. [9][10][11] Wang et al rstly employed tetramethylammonium T À /T 2 in acetonitrile/ethylene carbonate as electrolytes for DSSCs, resulting in a power conversion efficiency (PCE) of 6.4%.…”