Exploring the dynamic of Sn for the synthesis of high efficiency Cu2ZnSnSe4 based solar cells

Abstract

The need for new renewable sources of energy has been a reality for several years. Both because our current source of energy, fossil fuels, is limited, and because of the high pollution and problems associated with their use. As a solution to this problem, the development of renewable energies is our best asset. Within the wide range of possibilities, this work focuses on the energy that directly uses the enormous potential of our sun, photovoltaic energy. One of the most promising materials for emerging applications in the field of photovoltaics are the so-called kesterites, formed by the elements: Cu, Zn, Sn and Se; all of which are abundant and of low or null toxicity. The development of high efficiency cells based on kesterite faces several challenges related to the complex nature of this family of materials. Among them, the control of Sn that tends to form liquid and volatile species during the synthesis process having a strong exchange with the annealing atmosphere. In this work, the dynamics of Sn during the synthesis of the photovoltaic absorber, Cu2ZnSnSe4 (CZTSe), is investigated through a sequential process (Sputtering + Annealing). We compare the classical methodology where Sn is already incorporated in the solid precursor with a new and innovative solution in which Sn is partially incorporated in the vapour phase. The impact on the mechanism of CZTSe formation is investigated, as well as the properties of the layers and the characteristics of the finished devices