Temperature-Dependent Polarization Effects in Methylammonium Lead Iodide Field Effect Transistors

The recent progress in organo-metallic hybrid perovskite solar cells can be viewed as a highly significant historic event. The peak reported power conversion efficiency (PCE) has increased at an unprecedented rate, to a value now in excess of 22{\%},$^{\mathrm{1}}$ However many aspects of device operation remain poorly understood. Despite high reported carrier mobilities,$^{\mathrm{\thinspace }}$easily-accessible conduction and valence band energies and previous reports employing other organo-metallic hybrid perovkistes,$^{\mathrm{2}}$ field-effect transistors (FETs) based on methylammonium lead iodide (MAPbI$_{\mathrm{3}})$ have been scarcely studied. Using various electronic measurements, we here present a body of experimental evidence consistent with the existence of a mobile ionic species within the MAPbI$_{\mathrm{3}}$ perovskite. Temperature-dependent FET measurements reveal operating devices only below 210K. This is attributed to ionic screening of the semiconductor-dielectric interface. Temperature-dependent pulsed gate experiments, reveal a time-dependent source-drain current behavior consistent with this interpretation. Capacitors exhibit a decreasing low-frequency capacitance with temperature and a temperature-independent capacitance at higher frequencies. [1]www.nrel.gov/ncpv/images/efficiency\textunderscore chart.jpg [2]C. R. Kagan, et. al. Science 1999, \textbf{286}, 945.