ZnO-based dye solar cell with pure ionic-liquid electrolyte and organic sensitizer: the relevance of the dye–oxide interaction in an ionic-liquid medium

Abstract

The use of non-volatile electrolytes and fully organic dyes are key issues in the development of stable dye-sensitized solar cells (DSCs). In this work we explore the performance of ZnO-based DSCs sensitized with an indoline derivative coded D149 in the presence of a pure ionic-liquid electrolyte. Commercial nanostructured zinc oxide and an electrolyte composed of iodine plus (1) pure 1-propyl-3-methyl imidazolium iodide (PMII) and (2) a blend of PMII with low-viscosity ionic liquids were employed to construct the devices. Without further additives, the fabricated devices exhibit remarkable short-circuit photocurrents and efficiencies under AM1.5 simulated sunlight (up to 10.6 mA cm−2, 2.9% efficiency, 1 sun, active area = 0.64 cm2) due to the high surface area of the ZnO film and the high absorptivity of the D149 dye. Impedance spectroscopy is used to characterize the devices. It is found that the addition of the low-viscosity ionic-liquid improves the transport features (leading to a better photocurrent) but it does not alter the recombination rate. The robustness of the dye–oxide interaction is tested by applying continuous illumination with a Xenon-lamp. It is observed that the photocurrent is reduced at a slow rate due to desorption of the D149 sensitizer in the presence of the ionic liquid. Exploration of alternative ionic-liquid compositions or modification of the ZnO surface is therefore required to make stable devices based on ZnO and fully organic dyes.

Transient states and the role of excited state self-quenching of indoline dyes in complete dye-sensitized solar cells

“…On the contrary, for D149/TiO 2 cells we observed a drop of the photocurrent of the same magnitude that in D149/ZnO after 2 weeks instead of 2 h. Due to the measurements duration, all timeresolved studies of complete D149/ZnO cells presented in next sections correspond to the conditions at which the relative photocurrent (per absorbed photons) is about 10 times smaller than that of TiO 2 samples. We have checked that D149 dye molecules can be dissolved from ZnO film as indicated before [42]. As shown in Fig.…”

Charge collection properties of dye-sensitized solar cells based on 1-dimensional TiO2 porous nanostructures and ionic-liquid electrolytes

“…It has to be noted that more standard materials such as TiO 2 paste from Solaronix was found not to perform well with the organic dye and the ionic-liquid electrolyte utilized here. Incompatibilities between organic dyes and ionic-liquid electrolytes have been reported in the literature a number of times [39,50].…”

“…As mentioned, the use of 1-dimensional nanostructures to improve electron collection leads to lower light harvesting due to the diminution of surface area. The use of a fully organic dyes might produce desorption in the presence of ionic-liquid electrolytes [39]. To employ cobalt-based electrolytes, for which the efficiency record has been achieved [7], requires to look for alternative, more efficient dyes [40].…”

A novel 2,7-diaminofluorene-based organic dye for a dye-sensitized solar cell

“…Fig. 1 illustrates the structures of JD2 and D149 dyes, which is a very promising all-organic sensitizer for DSSCs, attracting a continuously growing interest as an alternative system to the commonly used Ru dye [32]. The JD2 dye contains 2,7-fluorenediamine which acts as a cascade donor system.…”