Enhancing the electrical performance of formamidinium perovskites through WS2 nanotubes incorporation

Abstract

Formamidinium-rich lead-halide perovskites combine strong optical absorption with low-temperature solution processing, but limited electrical conductivity can hinder charge extraction in optoelectronic devices. We investigate a composite approach in which hollow tungsten disulfide (WS2) nanotubes synthesized by a high-temperature vapor-gas-solid reaction are dispersed throughout Cs0.1FA0.9PbI2.9Br0.1 perovskite films. The nanotubes and composite films were examined by electron microscopy, x-ray diffraction, UV-visible spectroscopy, impedance spectroscopy, and conductive atomic-force microscopy. At an optimal WS2-nanotube concentration of 0.1mg mL-1, the perovskite retains its cubic photoactive phase and essentially unchanged optical response, while the dark conductivity increases by approximately two orders of magnitude. Conductive-AFM measurements independently show an approximately 2.5-fold increase in local current. Lower nanotube concentrations produce little measurable effect, whereas higher concentrations lead to aggregation and poorer film homogeneity. The results support a picture in which monocrystalline WS2 nanotubes create extended charge-transport pathways and favorable heterointerfaces without compromising light absorption, providing a practical route toward improved charge extraction in perovskite optoelectronic structures.