The primary energy supply in the EU is currently 80% dependent on fossil fuels. Reinventing the energy system based on a low carbon model is thus one of the critical challenges of the 21st Century. Solar energy is by far the largest of all carbon-neutral energy sources. More energy from sunlight strikes the Earth in one hour (4.3 × 1020 J) than all the energy consumed on the planet in a year (4.1 × 1020 J). Development of low-cost photovoltaic energy conversion technologies is thus of key importance.

Although organic semiconductor solar cells based on polymers or small-molecules have shown up to now modest cell efficiencies (around 10%), such a technological solution is really appealing since, through the years, it has shown rapid improvements in performance, which is now approaching that of amorphous silicon solar cells.

In particular, bulk heterojunction polymer solar cells (BHJ-SCs) represent a promising route to scalable, economically viable, energy conversion technologies when compared with conventional solar cells thanks to the potential for the development of low-cost, large-area cells and modules, e.g., by roll-to-roll production methods on flexible substrates.

Current state-of-the-art BHJ-SCs are typically fabricated on substrates with sputtered indium tin oxide (ITO) transparent electrodes, which unfortunately presents serious issues related to i) the release of oxygen and indium into the organic layer, ii) the poor transparency in the blue region, iii) its stiffness, which prevents its use in flexible solar cells, and iv) the large cost due to the limited supply of indium. All these aspects make the development and commercialization of a replacement for ITO a major focus in the BHJ-SCs Research and Development field.

The GO-NEXTS project, which addresses the call FP7-Energy-2012-1, in the topic Energy.10.2: Future Emerging Technologies, will focus its attention on new kind of electrodes based on doped, textured graphene electrodes, in order to increase the overall efficiency and performance of bulk heterojunction solar cells. This represents the first proposal to enhance light trapping in a solar cell by structuring one or more graphene contact electrode(s) to act as photonic crystal(s).
The proposal will leverage the combination of two different fabrication processes, i) graphene doping, to obtain semi-transparent electrodes, and ii) three-dimensional texturing of the electrodes.

The GO-NEXTS consortium will deliver significant innovations in transparent electrode materials, fabrication processes and device architectures in order to reach the ultimate goal of low-cost organic photovoltaic technologies. The following objectives will be targeted:

  • Development of fabrication and doping processes to realize stable monolayer graphene p- and n-doped electrodes with sheet resistances < 100 Ω/square and <10% change in sheet resistance over a period of 14 days. The stability of the electrodes within the encapsulated solar cells is foreseen to exceed one year
  • Development of organic photovoltaic cells with one or both electrodes fabricated from doped graphene
  • Development of processes for fabrication of nanostructured graphene-based photonic crystal electrodes targeting improved light trapping in the organic photovoltaic cells in the visible and/or near-infrared spectral ranges
  • Development and realization of graphene-based high-efficiency tandem solar cells
  • Development of experimentally validated models for the simulation of solar cells with graphene contacts, and distribution of the simulation tools implemented under BSD open-source license


Project Fact Sheet

Project Reference: 309201Duration: 36 months
Start date: 2012-11-01End date: 2015-10-31
Programme type: Seventh Framework ProgrammeContract type: Collaborative project


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