Probing Carrier Transport In Layered Perovskites With Nonlinear Optical And Photocurrent Spectroscopies

Interest in layered perovskite quantum wells is motivated by their potential for use in optoelectronic devices. In these systems, the smallest and largest quantum wells are most concentrated near opposing electrodes in photovoltaic cells. Coincident gradients in the energy levels and quantum well concentrations promote the funneling of electronic excitations and charge carriers through space. In this Perspective, we describe the development of several nonlinear optical techniques designed to elucidate the relaxation processes induced by light absorption in layered perovskite systems. Transient absorption microscopy provides insight into carrier diffusion and two-body recombination processes, whereas two-dimensional action spectroscopies are used to correlate elementary relaxation mechanisms to practical metrics of photovoltaic device performance. Our experiments suggest that charge carrier funneling processes do not facilitate long-range transport due to trapping. Rather, the bulklike phases of the films absorb light and transport carriers without participation of the smallest quantum wells.