Probing Ultrafast Excitonic Coherences and Charge-Generation Pathways in Quantum-Dot Photocells via Photocurrent-Detected Two-Dimensional Electronic Spectroscopy

Understanding how coherent excitonic states influence charge generation is essential for optimizing quantum-dot (QD) optoelectronic devices. Here, we apply photocurrent-detected two-dimensional electronic spectroscopy (PC-2DES) to a functioning CdSe QD photocell to track excitonic interactions and charge-separation dynamics under operational conditions. Selective excitation of the |1S⟩ manifold reveals strong contributions from red-shifted, delocalized excitons that dominate the photocurrent but contribute only weakly in optically detected 2DES. Global analysis uncovers three dynamical components, including a sub-100 fs process associated with photocurrent growth at specific spectral coordinates, consistent with rapid population transfer through delocalized states and possible trion formation. Unlike optical detection, PC-2DES suppresses longitudinal optical phonon signatures, enabling clear observation of higher-frequency beatings attributed to interdot electronic coherences. These results demonstrate the utility of PC-2DES for probing coherent charge-generation pathways in QD solids and for guiding the design of coherence-enabled optoelectronic devices.