Ultrafast two-Dimensional Electronic Spectroscopy of Millimeter-Sized Halide Perovskite Single Crystals

Halide perovskites (HaPs) have rapidly grown as highly promising photovoltaic materials. Despite the impressive device efficiencies, however, the fundamental mechanisms governing their unusual optoelectronic properties are still unclear [1]. In particular, the nature of their elementary optical excitations, their dynamics and interactions on ultrafast timescales are currently debated. Due to the comparatively low exciton binding energy, typically <; 50 meV[2], the near-bandgap absorption in HaPs is a mixture of excitons and free carrier transitions. This makes it challenging to distinguish the contributions of these two species to the nonlinear optical spectra in experiments, in particular at room temperature.