Abstract
The use of graphene‐based electrodes is burgeoning in a wide range of applications, including solar cells, light emitting diodes, touch screens, field‐effect transistors, photodetectors, sensors and energy storage systems. The success of such electrodes strongly depends on the implementation of effective production and processing methods for graphene. In this work, we take advantage of two different graphene production methods to design an advanced, conductive oxide- and platinum-free, graphene-based counter electrode for dye-sensitized solar cells (DSSCs). In particular, we exploit the combination of a graphene film, produced by chemical vapor deposition (CVD) (CVD-graphene), with few-layer graphene (FLG) flakes, produced by liquid phase exfoliation. The CVD-graphene is used as charge collector, while the FLG flakes, deposited atop by spray coating, act as catalyst for the reduction of the electrolyte redox couple (i.e. - and Co+2/+3). The as-produced counter electrodes are tested in both - and Co+2/+3-based semitransparent DSSCs, showing power conversion efficiencies of 2.1% and 5.09%, respectively, under 1 SUN illumination. At 0.1 SUN, Co+2/+3-based DSSCs achieve a power conversion efficiency as high as 6.87%. Our results demonstrate that the electrical, optical, chemical and catalytic properties of graphene-based dual films, designed by combining CVD-graphene and FLG flakes, are effective alternatives to FTO/Pt counter electrodes for DSSCs for both outdoor and indoor applications.
Highlights
Dye-sensitized solar cells (DSSCs)[1,2] represent an affordable photovoltaic (PV) technology, which recently achieved power conversion efficiency (PCE) > 14%[4]
Based on the advantages offered by the aforementioned graphene production and processing methods, we demonstrated a novel TCO and noble metal-free counter electrodes (CEs) based on chemical vapor deposition (CVD)-graphene/graphene flakes dual-film (Figure 1)
The nucleation of settings[214,215]).Raman spectroscopy analysis was graphene on Cu occurs primarily on the surface carried out to evaluate the structural properties of the asirregularities such as the rolling grooves and crystal produced materials
Summary
Dye-sensitized solar cells (DSSCs)[1,2] represent an affordable photovoltaic (PV) technology (production costs below 0.5 USD/Wp[3]), which recently achieved power conversion efficiency (PCE) > 14%[4] (certified PCE of 14.1%[5]). Polypyridine complexes of Co2+/Co3+ (coupled with donor-π-bridgeacceptor sensitizers)[73,74] show redox potential (> 0.4 V vs NHE[75,76]) more positive than the I3−/I− couple (0.35 V vs RHE[76,77,78,79,80]), allowing PCE over 12% to be achieved[4,46,71,72] (up to 14.3%[4]) Such results have been obtained by using current collectors of FTO, which are brittle[81] and whose fabrication requires high-temperature processes[82,83,84]. Pt-based CEs tend to degrade when exposed to the liquid electrolytes [88,89], affecting the lifetime stability of the cells [88,89]
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