Phase controlled synthesis of SnSe and SnSe2 hierarchical nanostructures made of single crystalline ultrathin nanosheets

The electronic and optoelectronic properties of tin selenide nanostructures are of great interest for application in energy conversion and storage devices. Despite the great progress achieved in nanoparticle synthesis, controlling the crystal phase in tin selenide nanostructures remains a challenge. In this article, we present a simple solvothermal approach for the phase controlled synthesis of SnSe and SnSe2 hierarchical nanostructures (HNs) for the first time. SnSe HNs have been prepared by reacting SnCl4 and SeO2 under solvothermal conditions using oleylamine as solvent. By adding a calculated amount of 1-dodecanethiol (1-DDT) to the reaction mixture the crystal phase can be tuned from SnSe to SnSe2. The obtained HNs were composed of single crystalline thin nanosheets with thickness in the range of 7-12 nm. A possible mechanism has been proposed for the phase controlled synthesis of tin selenides. The obtained SnSe and SnSe2 HNs showed good electrocatalytic activity in the redox reaction of the I-/I-3(-) shuttle. Dye sensitized solar cells (DSSC) employing SnSe and SnSe2 HNs as counter electrodes showed photovoltaic performances similar to the device made with a conventional platinum (Pt) counter electrode.