Incorporation of Germanium Nanoparticles in Organometal Perovskite Solar Cells

Metal-organic perovskite solar cells have gained much attention over the past decade. Known for its tunable bandgap via stoichiometric halide ratios, methylammonium lead halide (MAPbX₃) can be tuned from E_g = 1.6 eV (X = I) to E_g = 2.9 eV (X = Br). However, the Shockley-Queisser limit shows that an ideal solar cell under typical sunlight conditions should have a bandgap energy of 1.34 eV. Accessing the broader infrared range of the solar spectrum would allow for an increase in quantum efficiency. One well-known small bandgap semiconductor is germanium. However, unlike organometal perovskites, germanium is not cheaply or easily incorporated into the thin-film device structure. To combat this deficiency, we propose incorporating colloidal germanium quantum dots (Ge QDs), which may be solution processed, into our solar cell heterostructure to broaden our active layer’s absorption spectrum. QDs have the added benefits of having tunable sizes and ligands, allowing for optimizing device performance. In this work, we share the optical and optoelectronic results of incorporating monodispersed Ge QDs into our MAPbI₃ neat films and device architecture, respectively.