Ionic-to-electronic current amplification in hybrid perovskite solar cells: ionically gated transistor-interface circuit model explains hysteresis and impedance of mixed conducting devices - Moia, D; Gelmetti, I; Calado, P; Fisher, W; Stringer, M; Game, O; Hu, Y; Docampo, P; Lidzey, D; Palomares, E; Nelson, J; Barnes, PRF (Energy and Environmental Science, 2019)