Understanding electron transport on hybrid perovskite/carbon allotropes for energy conversion and storage applications: A first principles study

Photo-supercapacitors are combined devices that incorporate a photovoltaic cell as a light harvester unit to an electrical double layer capacitor where the charge carriers could be stored for further applications. Density functional theory calculations were performed to explore the electronic structure properties behind the mechanisms of electron communication between the interface of the solar cell material and the energy storage device. A hybrid perovskite was used to model the solar cell, while different carbon allotropes were considered as the molecular model of supercapacitor electrode. The communication of the perovskite with carbon is highly selective to the interaction of inorganic/organic termination and the carbon allotrope. Non-equilibrium Green's functions revealed the electron transmission behavior among the hybrid perovskite and the carbon allotropes, showing that the transport of charge carriers from the solar cell could be tuned with the adequate selection of the carbon allotrope. Quantum capacitance calculations were also performed to shed light into the intrinsic storage properties that the composite material may present. It shows that PbI and organic terminations in perovskite play a lead role to improve electronic charge retention, and consequently the inherent capacitance properties of the systems. This study also represents a combined theoretical/experimental work, in which an experimental methodology based on TEM graphics and XRD patterns allows to identify the inorganic/organic terminations in a hybrid perovskite solar cell material. This methodology could be implemented as a tool to tailor materials intended to improve the overall efficiency of a photo-supercapacitor device.