Synthesis, optical and photovoltaic properties of bismuth sulfide nanorods

Bismuth sulfide (Bi2S3) nanorods exhibit a low band gap, a high absorbance coefficient and good dispersity. In this study, the synthesis conditions of Bi2S3 nanorods were systematically investigated to obtain nanorods of a desired dimension, with high aspect ratios and good crystallinity. The as synthesized Bi2S3 nanorods, 37.2 nm in length and 6.1 nm in width, have a low band gap of similar to 1.4 eV with a conduction band and valence band of -3.8 eV and -5.2 eV, respectively. The nanorods were blended with poly(3-hexylthiophene) (P3HT) at a weight ratio of 1 : 1 to form a light harvesting P3HT : Bi2S3 hybrid film. The incorporated Bi2S3 nanorods can not only contribute light harvesting but also lead to a more ordered structure of the P3HT phase and a more efficient pi-pi* transition. Surface potential mapping of the hybrid film, measured by Kelvin probe force microscope (KPFM), shows a significantly negative shift (-34 mV) under white light illumination, which indicates carrier dissociation and the accumulation of negative charge on top of the hybrid film. The photovoltaic characteristics of the devices were also observed for those based on the P3HT : Bi2S3 hybrid film. This novel P3HT : Bi2S3 hybrid material provides a new candidate for the fabrication of low-cost and environmentally friendly polymer/inorganic hybrid solar cells.