Fractal microstructure of semiconducting Sb2S3 by surfactant-assisted spin coating and its advantage in optoelectronic properties

Antimony sulfide, Sb2S3 is a mixed band gap semiconductor having a great potential in photovoltaic applications. Its thin films and nanostructures are also a proven anode material in batteries and supercapacitors. This paper presents the synthesis of a unique fern-shaped fractal microstructure of Sb2S3 grown over bare glass substrate using a spin-coating assisted by Triton-X-100 surfactant. The FE-SEM images confirm the fractal formation spanning over hundreds of micrometers. The film exhibits a direct band gap of 1.62 eV. The photoluminescence spectra reveal a strong emission peak at 800 nm (1.55 eV) indicating radiative transitions from sub-band gap states. The surfactant, Triton-X-100, is found to be primarily responsible for forming the ‘Fern’ shaped fractals which have a fractal dimension of 1.84. Without the surfactant, a porous microstructure of Sb2S3 film is observed. The fractality is also associated with lower strain in the film leading to a reduced point defects which would otherwise act as potential recombination centers.