PhD Research Project: Elaboration and study of earth-abundant oxides based thin films for solar cel

PhD Thesis: Elaboration and study of earth-abundant oxides based thin films for solar cells

LMOPS - Université de Lorraine et Supélec, 2 rue E. Belin, 57070 Metz, France

Funding: Université de Lorraine (contrat doctoral)

Three years, Oct. 2019 to Sept. 2022

 

Thin-film solar cells technology is of considerable interest because of its potential to permit high photovoltaic conversion efficiencies and the relatively low development and production costs. The materials used up to now in this technology, and in particular the CdTe and CIGS chalcogenides (Cu2InGa (S, Se) 4), have made it possible to reach photovoltaic efficiency up to 20% for about fifteen years. However, these materials have major drawbacks: the scarcity of materials and in particular indium whose resources will no longer be sufficient to meet demand by 2030 and the toxicity of some of their elements (Cd). The alternatives proposed so far, and in particular those based on CZTS (Cu2ZnGa (S, Se) 4), have low photovoltaic efficiency, due in particular to the alloy disorder and the formation of defects, the impact of hetero-interfaces that are difficult to mastering, and difficulty in achieving and optimizing ohmic contacts.

The research work in this thesis concerns a family of materials with very high potential for photovoltaics, the oxides, with two main advantages. Using these materials allows, on the one hand, to design an all-oxide photovoltaic solar cell, from the absorber to the transparent contact and the buffer layer and, on the other hand, these materials contain only abundant elements and can be potentially developed using low-cost techniques. A solar cell all ZnO / ZnxGe1-xO / Cu2O oxide has been recently (2017) elaborated with a photovoltaic efficiency of 8.1%. In the case of copper oxide, one of the main keys that is the N doping. Recent research using the ZnGeO alloy as N-doped buffer layer show a very promising results. In addition, a nearby alloy, Cu2ZnGeO4 was recently (2017) elaborated for the first time, showing an optimal gap for photovoltaics. In this context, with the aim of developing thin-film solar cells based on abundant materials, we have set up the HECTOR project (for High EfficienCy Thin Films sOlaR cells), which this year received funding from CentraleSupélec and Université de Lorraine for the acquisition of a spray pyrolysis elaboration equipment. It is a low cost and very versatile technique, allowing the development of a large number of materials constituting the absorber, including oxides, the buffer layer and the transparent contact (TCO). Thus the entire solar cell structure can be realized with the same equipment.

This doctoral thesis within will concern the development of earth-abundant oxides, presented above, for solar cells. The final object if is the realization, characterization of an all-oxide solar cell with a complete ZnO / ZnxGe1-xO / Cu2O structure using the spray pyrolysis technique, and to develop the alloy Cu2ZnGeO4 which has never been developed by this technique (it was developed for the first time in 2017 by another very expensive technique).

The PhD work will be based on three pillars: (i) the development and optimization of spray pyrolysis elaboration processes; (ii) the structural and electrical characterization of the elaborated layers and devices; (iii) the realization of solar cell and the characterization of its performances. This thesis has a very high impact in terms of developing materials with high potential for photovoltaics and the study of their structural, optical and electrical properties and, ultimately, of solar cell realization. The expertise thus developed during this thesis can be valued both in academic research topics and in industry. The impact for the laboratory is also very high since this thesis, which will be the first of the HECTOR project, will participate in the development and consolidation of this research topic and the emergence of new projects and new collaborations.
 
Candidate Profile: Master's degree in physics or equivalent, good knowledge of the physics of semiconductors (materials and devices).

LMOPS - Université de Lorraine et Supélec, 2 rue E. Belin, 57070 Metz, France

The expertise developed during this thesis can be valued both in academic research topics and in industry. 

Funding source: université de Lorraine (contrat doctoral).

Master's degree in physics or equivalent, good knowledge of the physics of semiconductors (materials and devices), with a good ranking.

Sense of organization, autonomy, sense of teamwork.

Letter of motivation.

Interview with the selected candidates.

The selected candidates will also make a presentation to the laboratory council.

Final decision.