2, Rice University, Houston, Texas, United States
3, Northwestern University, Evanston, Illinois, United States
4, Université de Rennes 1, Rennes, , France
5, INSA de Rennes, Rennes, , France
Understanding and controlling charge and energy flow in state-of-the-art semiconductor quantum-wells has enabled high-efficiency optoelectronic devices. Two-dimensional Ruddlesden-Popper layered perovskites (RPPs) have recently emerged as an alternative to the classic bulk organic-inorganic hybrid perovskites, mainly due to significantly improved photo- and chemical-stability in optoelectronic devices . Few recent encouraging developments in optoelectronic applications, notably in energy harvesting and light emitting [1-3], have already been demonstrated in these two-dimensional layered perovskites. RPPs are solution-processed quantum-wells wherein the band gap can be tuned by varying the perovskite layer thickness, which modulates the effective electron-hole confinement. We report that, counterintuitive to classical quantum-confined systems where photo-generated electrons and holes are strongly bound by Coulomb interactions or excitons, the photo-physics of thin films made of Ruddlesden-Popper perovskites with a thickness exceeding two perovskite crystal-units (>1.3 nanometers) is dominated by lower energy states associated with the local intrinsic electronic structure of the edges of the perovskite layers . These states provide a direct pathway for dissociating excitons into longer-lived free-carriers that significantly improve the performance of solar cell devices.
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