Facile fabrication of low‐cost low‐temperature carbon‐based counter electrode with an outstanding fill factor of 73% for dye‐sensitized solar cells

Abstract

Summary Developing chemically inert, electrically conductive, and catalytically active counter electrodes (CEs) to replace conventional Pt‐based ones is highly desirable for dye‐sensitized solar cells. Herein, we reported a facile, cost‐effective, and low‐temperature synthesis pathway to develop carbon‐based CEs. The performance of homemade carbon paste (H‐CP)–based CE (H‐CE) was compared with that of commercial carbon paste (C‐CP)–based CE (C‐CE) and Pt‐based CE (Pt‐CE). The scanning electron microscope (SEM) results showed that H‐CE demonstrated a penetrable surface structure which facilitates the diffusion of electrolyte through the carbon electrode. This phenomenon enhanced the triiodide reduction with respect to C‐CE having a compact structure that limits the electrolyte diffusion. The charge transfer properties and catalytic activities of the investigated devices were explored using electrochemical impedance spectroscopy and Tafel polarization measurements; the obtained results indicated that the device based on H‐CE revealed relatively lower charge transfer resistance and higher exchange current density compared with C‐CE‐based device. The current‐voltage measurements showed that the device based on H‐CE has a power conversion efficiency of 2.70%, which was about 1.6 times higher than that of the device based on C‐CE (1.68%). Furthermore, a fill factor of 73% was achieved for the device based on H‐CE, which outperformed the Pt‐based device (69%) and was among one of the highest values obtained in the literature. Also, a tape adhesion test performed on H‐CP‐coated glass substrate displayed its excellent robustness.

Recent developments in metal‐free organic sensitizers derived from carbazole, triphenylamine, and phenothiazine for dye‐sensitized solar cells

“…The diffusion of the oxidized material (I 3 − ) to the cathode surface completes the chain. [8][9][10][11][12] From 1991 to now, the production of alternate cell materials, such as photoanodes, counterelectrodes, electrolytes, and sensitizers, has led to considerable improvement in DSSC's efficiency. DSSC efficiencies increased from 7.12% in 1991 to 14.3% in 2015.…”

“…Thus, recently many researchers have attempted to optimize DSSC materials to get high efficiency and also developed different materials to replace metal-free dyes, Pt, and liquid electrolyte to decrease the cost and increase the mechanical, electrochemical, and long-term stability of the DSSCs. 10,[19][20][21][22][23][24][25][26] In specific, sensitizers must have some essential characteristics for their effective performance, that is, a large and fast absorption from the visible to the near-infrared region, 27 chemical stability of the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) rates for the F I G U R E 1 Schematic illustration of DSSC [Colour figure can be viewed at wileyonlinelibrary.com] successful introduction of charges into the TiO 2, 28 and regeneration of the dye from the electrolyte, strong photostability, and solubility to prevent recombination. 29 On the other hand, Ru-bipyridyl compounds (N719, N3, and black dye) are the most effective dyes in the matter of performance.…”

“…The holes are reduced by the I − /I 3 − redox pair, and the oxidized dye is then regenerated by the I − species to create the I 3 − species. The diffusion of the oxidized material (I 3 − ) to the cathode surface completes the chain 8‐12 …”

Opaque Pt counter electrodes for dye‐sensitized solar cells

“…A typical device of DSSCs consists of photoanode, redox electrolyte media, dye, and counter electrode (CE) components. [5][6][7] A large number of experiments have been conducted by tailoring the properties of these components, focusing on the photovoltaic performance of DSSCs in the technological context. 8 For DSSCs, the performance of a CE is at least as critical as the performance of the other components.…”

Enhanced light harvesting in dye‐sensitized solar cells enabled by TiO 2 :Er 3+ , Yb 3+ upconversion phosphor particles as solar spectral converter and light scattering medium

“…Numerous studies have focused on enhancing the performance of DSSCs by optimizing various key components, including the photoelectrode, 4‐6 the photosensitizer, 7‐10 the redox electrolyte, 11‐13 and the counter electrode 14‐17 . Among these components, the photoelectrode has received particular attention because enhancing its properties can significantly improve the light‐energy absorption and harvesting capability.…”