Deposition of Sn-Zr-Se precursor by thermal evaporation and PLD for the synthesis of SnZrSe3 thin films

Background ABX3 (X=Se, S) chalcogenides are an emerging class of materials for sustainable photovoltaics. Among ABX3 materials, BaZrS3 has gained the highest community interest. BaZrS3 is the wide bandgap absorber (> 1.7 eV) and therefore is intended for application as a top sub-cell in multijunction devices. However, narrow band gap ABX3 compounds have drawn little attention although this could potentially open the path for fabrication of multijunction solar cells based entirely on ABX3 materials. SnZrSe3 is a narrow bandgap semiconductor with an absorption edge located at around 1.0 eV, but there are no reports on the formation of SnZrSe3 thin films thus far. In this work, therefore, we aim to obtain SnZrSe3 thin films by sublimation methods. Methods Thermal evaporation and pulsed laser deposition (PLD) techniques were used to deposit Sn-Zr-Se precursor films. SnZrSe3 powder was synthesized and used as a source material for evaporation and PLD target preparation. Precursor films were deposited by PLD from single-phase and binary selenide targets. Results We found that using SnZrSe3 powder, only SnSe films were deposited under various conditions by thermal evaporation. Precursor films obtained by PLD from single-phase targets were amorphous and comprised SnSe2 and a-Se phases whereas using binary targets crystalline SnSe and a-Se were detected. Thermogravimetric analysis revealed that SnZrSe3 was thermally stable up to 450 °C and afterwards decomposed into SnSe, Se and ZrSe2-x. Conclusions Using methods described in this work, we were not able to achieve congruent sublimation of SnZrSe3 because of the following reasons: (i) upon energetic excitation, SnZrSe3 decomposes into compounds with very different vapour pressure; (ii) inability to substitute O with Se due to very high chemical affinity of Zr and O. Direct sublimation methods are challenging for formation of SnZrSe3 thin films and other techniques, such as co-evaporation should be explored.