Solution-based synthesis and purification of zinc tin phosphide nanowires

Abstract

The solution-based synthesis of nanoscale earth-abundant semiconductors has the potential to unlock simple, scalable, and tunable material processes which currently constrain development of novel compounds for alternative energy devices. One such promising semiconductor is zinc tin phosphide (ZnSnP₂). We report the synthesis of ZnSnP₂ nanowires via a solution–liquid–solid mechanism utilizing metallic zinc and tin in decomposing trioctylphosphine (TOP). Dried films of the reaction product are purified of binary phosphide phases by annealing at 345 °C. Tin is removed using a 0.1 M nitric acid treatment leaving pure ZnSnP₂ nanowires. Diffuse reflectance spectroscopy indicates ZnSnP₂ has a direct bandgap energy of 1.24 eV which is optimal for solar cell applications. Using a photoelectrochemical cell, we demonstrate cathodic photocurrent generation at open circuit conditions from the ZnSnP₂ nanowires upon solar simulated illumination confirming p-type conductivity.