| 1. |
- Dembele, Kadiatou Therese, et al.
(författare)
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Graphene below the percolation threshold in TiO2 for dye-sensitized solar cells
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:6, s. 2580-2588
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a fast and large area-scalable methodology for the fabrication of efficient dye sensitized solar cells (DSSCs) by simple addition of graphene micro-platelets to TiO2 nanoparticulate paste (graphene concentration in the range of 0 to 1.5 wt%). Two dimensional (2D) Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirm the presence of graphene after 500°C annealing for 30 minutes. Graphene addition increases the photocurrent density from 12.4 mA cm-2 in bare TiO2 to 17.1 mA cm-2 in an optimized photoanode (0.01 wt% graphene, much lower than those reported in previous studies), boosting the photoconversion efficiency (PCE) from 6.3 up to 8.8%. The investigation of the 2D graphene distribution showed that an optimized concentration is far below the percolation threshold, indicating that the increased PCE does not rely on the formation of an interconnected network, as inferred by prior investigations, but rather, on increased charge injection from TiO2 to the front electrode. These results give insights into the role of graphene in improving the functional properties of DSSCs and identifying a straightforward methodology for the synthesis of new photoanodes.
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| 2. |
- Milan, Riccardo, et al.
(författare)
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ZnO@SnO2 engineered composite photoanodes for dye sensitized solar cells
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Layered multi-oxide concept was applied for fabrication of photoanodes for dye-sensitized solar cells based on ZnO and SnO2, capitalizing on the beneficial properties of each oxide. The effect of different combinations of ZnO@SnO2 layers was investigated, aimed at exploiting the high carrier mobility provided by the ZnO and the higher stability under UV irradiation pledged by SnO2. Bi-oxide photoanodes performed much better in terms of photoconversion efficiency (PCE) (4.96%) compared to bare SnO2 (1.20%) and ZnO (1.03%). Synergistic cooperation is effective for both open circuit voltage and photocurrent density: enhanced values were indeed recorded for the layered photoanode as compared with bare oxides (Voc enhanced from 0.39 V in case of bare SnO2 to 0.60 V and Jsc improved from 2.58 mA/cm2 pertaining to single ZnO to 14.8 mA/cm2). Improved functional performances of the layered network were ascribable to the optimization of both high chemical capacitance (provided by the SnO2) and low recombination resistance (guaranteed by ZnO) and inhibition of back electron transfer from the SnO2 conduction band to the oxidized species of the electrolyte. Compared with previously reported results, this study testifies how a simple electrode design is powerful in enhancing the functional performances of the final device.
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| 3. |
- Quesnel, Etienne, et al.
(författare)
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Graphene-based technologies for energy applications, challenges and perspectives
- 2015
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Ingår i: Current Opinion in Chemical Engineering. - : IOP Publishing. - 2211-3398. ; 2:3, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Here we report on technology developments implemented into the Graphene Flagship European project for the integration of graphene and graphene-related materials (GRMs) into energy application devices. Many of the technologies investigated so far aim at producing composite materials associating graphene or GRMs with either metal or semiconducting nanocrystals or other carbon nanostructures (e.g., CNT, graphite). These composites can be used favourably as hydrogen storage materials or solar cell absorbers. They can also provide better performing electrodes for fuel cells, batteries, or supercapacitors. For photovoltaic (PV) electrodes, where thin layers and interface engineering are required, surface technologies are preferred. We are using conventional vacuum processes to integrate graphene as well as radically new approaches based on laser irradiation strategies. For each application, the potential of implemented technologies is then presented on the basis of selected experimental and modelling results. It is shown in particular how some of these technologies can maximize the benefit taken from GRM integration. The technical challenges still to be addressed are highlighted and perspectives derived from the running works emphasized.
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| 4. |
- Selopal, Gurpreet Singh, et al.
(författare)
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Graphene as transparent front contact for dye sensitized solar cells
- 2015
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 135, s. 99-105
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Tidskriftsartikel (refereegranskat)abstract
- A transparent conductive graphene film is investigated as front contact in dye-sensitized solar cells (DSSCs), as an alternative to traditional transparent conducting oxides (TCO). The film is composed of poly-crystalline few-layers graphene, covering homogeneously an area of 1 cm2, deposited by chemical vapour deposition (CVD) technique on larger area Cu catalyst substrate and transferred on glass. DSSC photoanode is then fabricated, according to consolidated procedure, by sequential casting of TiO2 films through tape casting technique, followed by annealing at 500 °C, and sensitization with N719 dye. An outstanding value of photoconversion efficiency as high as 2% is recorded for the best cell, under one sun irradiation (AM 1.5 G, 100 mW cm−2), which is the highest ever reported for this kind of devices using graphene as front conducting film. Compared to previous results in the literature, the application of a large area continuous graphene film, guaranteed by the CVD deposition, definitely outperforms graphene layers composed by smaller graphene platelets (at micrometer scale). Morphological and electrical characterizations of graphene are reported and the functional performances of the best cell are compared with those obtained from classical DSSC exploiting fluorine-doped tin oxide. Obtained results encourage further investigation of graphene homogeneous thin film as viable alternative to standard TCOs for application in advanced devices, requiring high temperature processing or flexible substrates, incompatible with standard TCO films.
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