Lead halide perovskites have been extensively studied to explore their photovoltaic properties. They offer a useful strategy for continuous tuning of the semiconductor bandgap. In addition to photovoltaic applications these lead halide perovskites offer rich photophysical properties with ability to induce electron and hole transfer at the semiconductor/electrolyte interface. The photoinduced electron transfer between CsPbBr₃ quantum dots and methyl viologen shows electron transfer to be completed with 20 ps. The transient absorption spectroscopy and emission spectroscopy offers mechanistic and kinetic insights of the interfacial charge transfer processes. CsPbBr₃ films cast from colloidal suspension can also be transformed into CsPbI₃ via a halide exchange reaction upon exposure to a heated PbI₂ solution (~70°C). The internal structure of hybrid CsPbBr_xI_3-x varies with increasing thickness of the exchanged film. The gradient structure thus allows us to probe the flow of the charge carriers within the film. The electron transfer properties that highlight photocatalytic properties of mixed halide nanocrystals will be discussed.