3D hierarchical FeSe2 microspheres: Controlled synthesis and applications in dye-sensitized solar cells

Mastery over the structures at nano/microscale can effectively tailor the catalytic activity and durability of materials. Herein, three dimension (3D) hierarchical iron diselenide (FeSe 2 ) microspheres have been successfully synthesized via a hot-injection method. The morphologies of building blocks and final products can be simply controlled by the amount and/or the type of alkythiols, from irregular micro/nanoparticles to uniform 3D hierarchical microspheres made of ultrathin nanosheets or rhombus-like nanorods . A formation mechanism has been understood based on the inherent crystal structure of FeSe 2 and the selective adsorption of alkythiols. The as-obtained FeSe 2 samples were employed as counter electrode (CE) materials in dye-sensitized solar cells (DSSCs). Electrochemical characterizations indicated that the 3D hierarchical FeSe 2 microspheres composed of ultrathin nanosheets (FeSe 2 NSs) exhibited low charge transfer resistance at the electrolyte–electrode interface, high electrocatalytic activity and fast reaction kinetics for the I − /I 3 − redox reaction . A DSSC with FeSe 2 NSs CE achieved a high power conversion efficiency of 8.39% under a simulated solar illumination of 100   mW   cm −2 (AM 1.5), comparable to that of Pt based devices (8.20%). Moreover, the fast activity onset and relatively long stability demonstrated that the FeSe 2 NSs is a promising alternative to Pt in DSSC.