Perovskite solar cells are attracting lots of attention because as a new solar cell material perovskite has the potential to beat the performance of conventional Si devices at lower cost. This paper looks very carefully at the Pb to I ratio in the lead iodide used as one of the starting materials used to make the most commonly studied perovskite (methylammonium lead iodide). This is of significance because it provides an insight into why there is such variability in the many different ‘optimal’ formulations reported in the literature. Subtle differences in the stoichiometry of the starting materials used in the preparation of the most ubiquitous perovskite material for solar applications has huge ramifications for the performance of the devices made. We also propose processing routes which help minimize the impact of these stoichiometric variations through well controlled planetary ball milling to produce stoichiometric PbI2 and microcrystal formation which has the effect of correcting any non ideal perovskite stoichiometry by removing excess materials in a suitable solvent wash.
Read Dr Dunbar's new paper,