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A full plasma and vacuum integrated process for the synthesis of high efficiency planar and 1D conformal perovskite solar cells

Periodic Reporting for period 1 - PlasmaPerovSol (A full plasma and vacuum integrated process for the synthesis of high efficiency planar and 1D conformal perovskite solar cells)

Reporting period: 2016-01-01 to 2017-12-31

"The increasing costs of the fossil fuels together with their environmental harm are encouraging the science community and companies to develop efficient ways to use the available renewable resources. Photovoltaic or solar cells (SC) devices –that transform light into electricity- have been extensively studied in the last decades since they represent a promising way to exploit the sun energy. Currently, perovskite-based SC are receiving increasing attention due to their low cost and high efficiency. First results appeared less than 10 years ago related with Dye-Sensitised Solar Cells. Currently, Perovskite-based solar cells are mostly fabricated via wet methods in planar architecture. Perovskite SC are very promising as an alternative for the existing ones, but still need to advance to reach higher efficiency and durability and require synthesis methods compatible with the industrial production of CMOS devices at wafer scale. Inherent to the nature of the wet approaches, usually appear several drawbacks as contaminations and chemical reactions on the interfaces that might result deterioration of the SC performance and therefore should be avoided. The improvement of crucial aspects of the cells requires a clean alternative approach allowing the fabrication of the different components of the SC device in an integrated sequential process in one-single reactor.
PlasmaPerovSol main objective is the fabrication of a complete perovskite solar cell device by a full plasma and vacuum integrated process carried out under the premises of the “one reactor"" concept. Plasma and vacuum processes present as advantage the high purity and stoichiometric control on the deposition within an ample range of materials compositions (organic, inorganic, hybrid, gradient compositions). The synthesis approach is compatible with large scale industrial production and the low temperatures used make the approach compatible with current CMOS technology.
The research developed has fulfilled many of the objectives proposed. We have developed the proposed methodology, setting up all the experimental procedures for the fabrication of a complete solar cell in “one reactor”. The materials deposited by this plasma/vacuum protocol have been be compared with the ones deposited by wet methods and has enabled the understanding of the performance of every vacuum deposited layer. Another unprecedented objective fulfilled is the fabrication of conformal deposits over different templates. The final demonstration of the approach has been realised by the deposition of a complete perovskite solar cell in a 1D-core@multishell architecture (see Figure).
The work performed during the project comprised the following:
Months 1-4. Design, assembly and testing of a vacuum and plasma reactor to synthesize all the layers required. At the beginning of the project it turned out to be necessary to construct this fully dedicated system for the perovskite SC fabrication due to the incompatibility of one of the precursors used (Methylammonium Iodide) with other materials. In addition, the reactor was connected to a glove box in order to avoid the atmospheric contact of the moisture and/or oxygen sensitive materials.
Months 5-20. WP1. Development of the nanoarchitectures. This WP was dedicated to the fabrication of the different layers over planar and 1D-Nanostructures as well as their characterization. In this WP it was studied the Conductive Substrate and Template conductive material(WP1.1) the Electron Transporter layers(WP1.2) the Perovskite Absorber and Hole transporter(WP1.3) and the Final Transparent Electrode(WP1.4). For this period it was crucial the involvement of the group of Prof P. Midgley at the Univ. of Cambridge, United Kingdom (Secondment 2) that performed high resolution TEM characterization.
Months 21-24. WP2. Characterization of the SC fabricated in WP1. This WP was performed in the Laboratory of Prof. J.A. Anta at the Univ. Pablo de Olavide, Seville, Spain (Secondment 1) as well as the comparison between 2D- and 1D-SC performance. In order to elucidate the influence of every layer fabricated by vacuum and plasma methodology, we combined them with the rest of the layers fabricated by a wet approach.
Exploitation and dissemination. WP4 has been allocated during the entire project. Due to the delay suffered during the first months and to the high amount of results, the future publications, conferences or other related activities will adequately acknowledge PlasmaPerovSol project.
The dissemination of the results of the projects has been performed through different media:
- Peer Review publications. 6 accepted papers in high impact journals, including 2 journal covers. 2 additional publications are under revision. Currently other publications are being prepared (7 will be sent soon)
- Conferences. 7 communications to international conferences or symposiums.
- Outreaching activities.
The complete list of dissemination activities as well as the main scientific results achieved can be found in the technical Report.
PlasmaPerovSol aimed the development of novel synthetic strategies of perovskite solar cells architectures. All the synthetic procedures studied are energy efficient and directly scalable at industrial fabrication. In addition, the synthetic steps are solvent free and environmentally friendly without any kind of measurable emission of liquid or gaseous contaminants during all the fabrication cycle of the novel solar cell devices.
The plasma assisted vacuum technique proposed developed in PlasmaPerovSol has allowed the deposition of very homogeneous conformal layers of every SC component with a fine control on the thickness, crystallinity and nanostructure. A wide range of microstructures have been achieved for all the layers deposited. In addition, the plasma assisted methodology have permited the deposition of conformal layers over one-dimensional structures. We have succeeded in the fabrication of a complete cell in a 1D-core multishell structure by a series of integrated synthetic steps. This unprecedented nanoarchitecture will soon demonstrate the advantages of 1D structuration such as higher efficiency, broadband absorption, anti-reflection or self-cleaning capabilities, for future photovoltaics.