Extending the Breadth of Metal Halide Perovskite Applications to the Control and Modulation of Light

The rapid rise of metal halide perovskites as photovoltaic materials has been an impressive achievement. Their performance as solar energy harvesters stands out amongst solution processed materials. Metal halide perovskites have also emerged as efficient light emitters for potential use in light emitting diodes and lasers. Their promise derives from a combination of their solution processing, desirable optical and electronic properties, and compositional flexibility. Perovskites can be engineered to have sharp absorption onsets, high photoluminescence quantum yields, and low trap state densities. In this thesis I present applications of metal halide perovskites in the control and modulation of light. I expand their applicability by exploiting nonlinear and electro-optic processes in these materials. I begin by investigating the electro-optic behaviour of germanium halide perovskites. The electro-optic coefficients of these compounds are calculated using density functional theory. CsGeI3 is predicted to have an electro-optic coefficient of 47 pm·V-1 at the communications wavelength of 1550 nm, exceeding the greatest coefficient of lithium niobate. This study is the first exploration of the linear electro-optic process in metal halide perovskites. Next, I study quantum-confined Stark effects in layered perovskites. Electroabsorption spectroscopy is conducted with thin films of two-dimensional metal halide perovskites featuring either methylammonium or cesium cations bound in the quantum well structures. While the cesium compounds display conventional energetic red-shifts, methylammonium compounds exhibit blue-shifts. These anomalous blue-shifts are attributed to extraordinary weakening of the exciton binding energy ultimately induced by polarization of the methylammonium dipoles. Both the red-shifts and blue-shifts are engineered to produce modulations in the amplitude of the absorption coefficient of 70 cm-1 for 56 kV·cm-1 applied fields, the strongest modulation amplitudes reported for solution processed materials at room temperature. Lastly, I characterize two-photon absorption in methylammonium lead bromide perovskite crystals. I determine the nonlinear absorption coefficient, along with its polarization dependence. A two-photon absorbing photoconductor was fabricated to autocorrelate ultrafast laser pulses and demonstrate the applicability of this process in metal halide perovskites.Ph.D