1. Could you explain the significance of your article to the non-specialist? 

There is growing interest in low temperature, low-cost soft-chemical synthetic routes to semiconductor materials, often as thin films, in particular for use in solar cells. Bismuth sulfide is an excellent solar absorber material and has attracted considerable interest for many other applications, as evidenced by the volume of publications associated with the material in recent years. We have developed a simple, single-step process for growth of thin films of crystalline solar absorber layers based on bismuth sulfide, from aqueous solutions at room temperature.

2. What has motivated you to conduct this work? 

Environmental and ultimately commercial considerations necessitate the replacement of toxic heavy metals (e.g. Cd, Hg) and chalcogenide sources used in many in compound semiconductor solar cell technologies.   Solution deposition routes using aqueous precursors are highly attractive as they require simple apparatus, are compatible with sensitive substrates (e.g. polymers) and often can be scaled up to production volumes with relative ease.   However, for practical use in functional devices, it is often necessary to anneal the as-deposited materials, to effect complete crystalline conversion, thus eliminating the low-temperature advantage of CBD over vapour phase methods, like e.g. CVD. Our process deposits crystalline thin films at room temperature.   

3. Where do you see this work developing in the future? 

The simplicity of the approach in general provides potential for development of advanced materials with limited resources, using a single-step "one-pot" protocols with reduced energy consumption and environmentally benign precursors, thus appealing to chemists and others in the field and enabling further interdisciplinary studies.  Photoelectrochemical solar cells based on layers of n-type doped and intrinsic Bi2S3 are expected to increase light harvesting and provide sufficient band-bending at the semiconductor-electrolyte interface, with potential for increased device efficiencies.

4. Are there any particular challenges facing future research in this area? 

To accelerate commercialisation, fabrication of photovoltaic devices using "soft-chemical" methods on polymer substrates is highly desirable.  It will also be important to develop robust encapsulation technologies to protect such devices from stresses imposed by the environment.