  The presence of mobile ions in perovskites is well known to influence the
device electrostatics leading to a wide variety of anomalous characteristics
related to hysteresis, efficiency degradation, low frequency capacitance, large
signal switching, etc. Accordingly, the ion mobility is understood to a have a
critical influence on the associated time constants/delays. Quite contrary to
this broadly accepted thought, here we show that the time delays associated
with large signal switching show a universal behavior dictated by electronic
dipoles, rather than ionic dipoles. Due to the resultant sudden and dramatic
collapse of contact layer depletion region, switching delays are independent of
ion mobilities! Further, our detailed numerical simulations, well supported by
experimental results, indicate that terminal currents show near steady state
behavior well ahead of the relaxation of ionic distributions to their steady
state conditions. These results have interesting implications towards the
understanding and optimization of perovskite based electronic devices,
including solar cells and LEDs.
