Researchers at University College London, UK, have reassessed the validity of the 'tolerance factor' (a decades-old indicator for the stability and distortion of crystal structures), used in predicting new hybrid perovskite structures. The results of their work may cast shadows on the optimism that surrounds perovskites' future uses.

Recent studies out of Cambridge University showed that the tolerance factor approach worked well at assigning radii to organic ions in a wide range of hybrid perovskites. They suggested that there could be more than 600 undiscovered hybrid perovskites. The UCL team was interested in whether the tolerance factor approach was still valid for halide perovskites suitable for solar cells. The chemical properties of the heavy iodide anions in these structures are very different to the hard atomic spheres assumed in tolerance factor calculations. The results suggested that ‘the tolerance factor simply doesn’t work for iodide perovskites.’

Solliance announced a 10% aperture area power conversion efficiency for its up-scaled thin-film perovskite photovoltaic modules. The efficiency was measured on an aperture area of 168 cm2. Twenty-five cells were serial connected through an optimized P1, P2, P3 interconnection technology. The PV module was realized on a 6x6 inch2 glass substrate using industrial scale-able slot die coating in combination with laser patterning.

Based on previous optimization on 16 cm2 modules, the Solliance team was able to transfer this to a 6x6 inch2 sized glass substrate using the developed blade coating process and the optimized mechanical patterning technology. These results demonstrate the up-scalability of this new thin film PV technology. Apart from the electrodes currently used, all layers can be processed in ambient environment and at temperatures below 120⁰C. Furthermore, the deposition and interconnection technologies used for obtaining these results are industrially available for Sheet-to-Sheet as well as for Roll-to-Roll manufacturing. The latter allows for creating high volume production in the future.