  With excellent efficiencies being reported from multiple labs across the
world, device stability and the degradation mechanisms have emerged as the key
aspects that could determine the future prospects of perovskite solar cells.
However, the related experimental efforts remain scattered due to the lack of
any unifying theoretical framework. In this context, here we provide a
comprehensive analysis of ion migration effects in perovskite solar cells.
Specifically, we show, for the first time, that (a) the effect of ionic charges
is almost indistinguishable from that of dopant ions, (b) ion migration could
lead to simultaneous improvement in Voc and degradation in Jsc - a unique
observation which is beyond the realm of mere parametric variation in carrier
mobility and lifetime, (c) champion devices are more resilient towards the ill
effects of ion migration, and finally (d) we propose unique characterization
schemes to determine both magnitude and polarity of ionic species. Our results,
supported by detailed numerical simulations and direct comparison with
experimental data, are of broad interest and provide a much needed predictive
capability towards the research on performance degradation mechanisms in
perovskite solar cells
