Metal halide perovskite (MHP) solar cells are of interest in the development of low cost, high efficiency solar panels and are usually studied by subjecting the material to degradation analysis. In their paper, Penukula et al. set out to develop a new method to directly quantify the ion migration in terms of mobile ion concentration (Nₒ) and ionic mobility (µ). The researchers used a Linkam LTS420E-PB4 stage, which incorporates a temperature control element and positional tungsten probes, to study the effect of temperature on MHP performance and conduct electrical measurements. Their study demonstrates that Nₒ has a larger impact on device stability than µ. The researchers also studied the effect of small alkali metal cation additives on ion migration and found that the choice of top electrode in MHP solar cells has a greater influence on Nₒ than moisture or cation additives.