MAPLE · Multidimensional generAtion of bulk Photovoltaic currents by vectorial Light Engineering

Replacement of fossil fuels with renewable energy sources is one of the main challenges of our time. Harvesting solar radiation is a possible solution, as the sunlight power reaching Earth is orders of magnitude larger than human consumption. However, the efficiency of photovoltaic solar cells is limited by dissipation of all the photons energy exceeding the semiconductor bandgap according to the Shockley-Queisser (SQ) limit. The bulk photovoltaic (BPV) effect arising in non-centrosymmetric crystals has attracted considerable attention as above-bandgap electrons are predicted to contribute to the photocurrent, thus breaking the SQ limit. To enhance BPV-device efficiencies the underlying tensorial light-matter interaction needs further attention. Until now, the contribution from the three-dimensional shape of the electromagnetic field has been neglected, while a greater emphasis has been placed on the effect of the in-plane field gradient. A comprehensive theoretical and experimental understanding of the vectorial coupling between the conductivity tensor and the three-dimensional field structure is thus far lacking. The goal of this proposal is to identify the mechanism governing this coupling through carefully engineered light beams and by nanoscale mapping of the photocurrent with a novel scanning probe technique. This knowledge will be used to develop an optimization algorithm to improve BPV-devices efficiency: given a target material it will return the light structuring which maximizes the photocurrent generation. During the project I will complement my skills in scanning probe techniques, optics and solid-state physics with methods in structured light and materials science/engineering. This unique set of skills will enable the progress of my career in the emerging field of structured light-matter interactions. At the same time, I will acquire the necessary transferrable skills (leadership, communication and grant writing) to become an independent group leader.