  Despite the widespread use of solution-processable hybrid organic-inorganic
perovskites in photovoltaic and light-emitting applications, determination of
their intrinsic charge transport parameters has been elusive due to the
variability of film preparation and history-dependent device performance. Here
we show that screening effects associated to ionic transport can be effectively
eliminated by lowering the operating temperature of methylammonium lead iodide
perovskite (CH3NH3PbI3) field-effect transistors (FETs). Field-effect carrier
mobility is found to increase by almost two orders of magnitude below 200 K,
consistent with phonon scattering limited transport. Under balanced ambipolar
carrier injection, gate-dependent electroluminescence is also observed from the
transistor channel, with spectra revealing the tetragonal to orthorhombic phase
transition. This first demonstration of CH3NH3PbI3 light-emitting FETs provides
intrinsic transport parameters to guide materials and solar cell optimization,
and will drive the development of new electro-optic device concepts, such as
gated light emitting diodes and lasers operating at room temperature.
