Mobile ions in hybrid perovskite semiconductors introduce a new degree of freedom to electronic devices suggesting applications beyond photovoltaics. An intuitive device model describing the interplay between ionic and electronic charge transfer is needed to unlock the full potential of the technology. We describe the perovskite-contact interfaces as transistors which couple ionic charge redistribution to energetic barriers controlling electronic injection and recombination. This reveals an amplification factor between the out of phase electronic current and the ionic current. Our findings suggest a strategy to design thin film electronic components with large, tuneable, capacitor-like and inductor-like characteristics. The resulting simple equivalent circuit model, which we verified with time-dependent drift-diffusion simulations of measured impedance spectra, allows a general description and interpretation of perovskite solar cell behaviour. Broader contextHighly efficient solar cells made using hybrid perovskite semiconductors may prove commercially viable. The success of these cheap materials is in part due to their ability to I.G., D.M. and P.B. initiated the project led by P.B. D.M. measured devices fabricated and developed by M.S., O.G., H.H., D.L. and P.D.; I.G. performed the simulations on software developed with P.C.; D.M. and P.B. developed the transistor description and circuit models; W.F. and D.M. performed the equivalent circuit fitting using circuit models coded by P.B. All authors discussed the results and participated in preparation of the manuscript drafted by P.B, D.M. I.G. and P.C.

A Cu-exchanged SSZ-39 zeolite has been synthesized and tested for the selective catalytic reduction (SCR) of NOx. This material shows an excellent catalytic activity, and most importantly, an extraordinary hydrothermal stability.