Two-dimensional coherent photocurrent excitation spectroscopy in a polymer solar cell

In high-performance solar cells based on polymeric semiconductors, the mechanism of photocarrier generation on $<100$-fs timescales is yet to be unravelled. In particular the dynamics of early-time electronic coupling between excitons on polymer chains and charge-transfer states need to be investigated in order to develop a detailed picture of ultrafast processes involved in photocurrent production. In this proceeding, we report preliminary measurements using a novel spectroscopy that can measure such correlations: two-dimensional coherent photocurrent excitation spectroscopy. This nonlinear technique measures off-diagonal spectral correlations in a two-dimensional photocurrent excitation spectrum. We interpret these sectroscopic measurements in light of recent theoretical predictions.