Solution-Processed BiI Films with 1.1 eV Quasi-Fermi Level Splitting: The Role of Water, Temperature, and Solvent during Processing.

We present a mechanistic explanation of the BiI film formation process and an analysis of the critical factors in preparing high-quality solution-processed BiI films. We find that complexation with Lewis bases, relative humidity, and temperature are important factors during solvent vapor annealing (SVA) of films. During SVA, water vapor and higher temperatures limit the formation of the BiI-dimethylformamide coordination complex.

Nanoscale surface potential variation correlates with local S/Se ratio in solution-processed CZTSSe solar cells.

Thin film solar cells made from Cu, Zn, Sn, and S/Se can be processed from solution to yield high-performing kesterite (CZTS or CZTSSe) photovoltaics. We present a microstructural study of solution-deposited CZTSSe films prepared by nanocrystal-based ink approaches using scanning probe microscopy (SPM) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). We correlate scanning Kelvin probe microscopy (SKPM) maps of local surface potential with SEM/EDS images of the exact same regions of the film, allowing us to relate observed variations in surface potential to local variations in stoichiometry.