Carbon-Based Perovskite Solar Cells: Interface Engineering of 5-AVAI Additive

Perovskite materials have great potential for high efficiencies in photovoltaic devices, with the best performances exceeding 26% in a single junction. We now need to further develop perovskite device architectures that combine ease of industrial development with effective durability. Among the alternatives, mesoporous frameworks based on metal oxide and carbon are promising due to their inherent high stability. In the presented work, two perovskite formulations will be compared: MAPbI 3 and (5-AVA) x MA 1-x PbI 3 . Both were infiltrated using drop casting as a final step, which provides a clean industrial process for large scale and stable perovskite devices. The aim was to highlight the differences in behavior between devices based on the traditional MAPbI 3 perovskite when fabricated with or without 5-ammonium valeric acid iodide (5-AVAI) as an additive. A detailed study with a large series of characterizations (macroscopic functional properties, LBIC imaging, photoluminescence, UV-visible spectroscopy, X-ray diffraction, impedance spectroscopy) has provided new insights into how carbon-based mesoscopic perovskite solar cells perform and degrade. Perovskites based on AVAI possess higher performances and durability than the original perovskite formulation, however they also demonstrated a higher potential for species diffusion and interface contamination. A special attention will be thus given to the method used to measure performances by analyzing J-V curves at different scan rates. Indeed, this allowed us to define boundary conditions allowing the observation of two different states within our devices (defined as ‘stable’ and ‘metastable’). This behavior was interpreted as a structural transition [1] and can vary according to the perovskite formulation. In addition, the degradation of performance with aging time under damp-heat conditions was found related to a different mechanism in devices formulated with or without AVAI: the critical damage occurring either at the perovskite interfaces or within the perovskite itself. References: [1] De Moor, G.; Charvin, N.; Farha, C.; Meyer, T.; Perrin, L.; Planes, E.; Flandin, L. Understanding the Anomalous J–V Curves in Carbon-Based Perovskite Solar Cells as a Structural Transition Induced by Ion Diffusion. Solar RRL 2024 , 2300998.