Hierarchical CuInS₂ synthesized with the induction of histidine for polymer/CuInS₂ solar cells

Hierarchical CuInS₂ (H-CuInS₂) was synthesized with the induction of histidine by the solverthermal method. The factors such as the category of the amino acid, the molar-quantity of histidine, the solvent, reaction time and reaction temperature were observed. The products were characterized by scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and ultraviolet-visible absorption spectrum. The results showed that, histidine is proven to be effect to synthesize the uniform flower-like chalcopyrite H-CuInS₂ in the solvent of N,N-dimethyl formamide at 180 °C for 24 h, which is originated from the strong coordinate ability of histidine. The change in the molar-quantity of histidine would result in the obviously different sizes and micro-structures of H-CuInS₂, contributing to the different light-harvesting ability and fluorescence quenching efficiency to poly (2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV). As a result, polymer solar cells with MEH-PPV and different H-CuInS₂ displayed structure-dependent device performances, device based on small-sized H-CuInS₂ obtained higher energy conversion efficiency of 0.59% under the monochromatic illumination of 15.85 mW/cm² with wide spectrum response from 300 to 900 nm.