Solution-processed mesoscopic Bi₂S₃: polymer photoactive layers

The fabrication of solution-processed nontoxic mesoporous Bi₂S₃ structures is demonstrated and the suitability of these structures for use in hybrid solar cells investigated. Mesoporous Bi₂S₃electrodes are prepared via thermal decomposition of a thin film composed of a bismuth xanthate single source precursor. The resultant Bi₂S₃films are made up of regular needles with approximate dimensions of 50×500 nm, as confirmed by scanning electron microscopy (SEM). The crystallinity of the Bi₂S₃ is found to be dependent on the annealing temperature, as determined by X-ray diffraction. The porous Bi₂S₃ films are infiltrated with the hole conductor P3HT to generate novel hybrid films, and laser-based transient absorption spectroscopy is used to interrogate the charge-separation reaction at the resulting Bi₂S₃/P3HT heterojunction. Specifically, optical excitation of the hybrid films results in efficient and long-lived charge separation (microsecond to
millisecond timescale), thereby rendering such films suitable for the development of novel low-cost solar-energy conversion devices.